Legal status of units of electric measure in the U.S
<p>From 1894 until 2006, the United States Code had a section that defined the units of electrical measure (i.e. the volt, the ampere, etc.; see the Appendix for details). These sections were repealed in 2007, and it <em>seems</em> they haven't been replaced by any other law or regulation. However, the act that repealed them said it did so on the basis of those sections being 'redundant and obsolete authority'.</p>

<p><strong>My question in a nutshell</strong></p>

<p>Suppose the year is 2002, and a utility company decides to change all its documents, contracts, etc. so that everything is expressed in e.g. <a href="https://en.wikipedia.org/wiki/Statvolt" rel="nofollow noreferrer">statvolts</a> and statamps. In 2002, 15 U.S.C. 223 and 224 might have been interpreted as saying that this company can't do that, and that a judge might order it to start using volts and amps. </p>

<p>(See also this <a href="https://law.stackexchange.com/questions/52178/us-code-used-to-say-the-unit-of-electric-current-shall-be-the-ampere-what-leg">related question</a>.)</p>

<p>What about now? If the company tries to do business in statvolts and statamps now, is there any <em>general</em> federal regulation about units of electrical measure, presumably set by the Department of Commerce, that the company would be violating?</p>

<p>Or are there now only activity-specific regulations? For example, it could be that while there is no general law about electric units like there existed until 2007, there is still a mass of regulations about e.g how a power plant is supposed to conduct this or that aspect of its business, and perhaps in those regulations there are many statements such as <em>the contract should specify the output potential (in <strong>volts</strong> or <strong>kilovolts</strong>)…,</em> etc. Is that what the legal status of the volt and the ampere is like—there is no longer one place that sets them as legal units once and for all, but rather they are simply matter-of-factly used in all particular regulations. One might say this would make them <strong>de facto</strong> legal units.</p>

<p>So here is yet another way to summarize my question: post 2007, are the volt, the ampere etc. still formally—in some federal law or regulation—declared to be legal units in general, or are they now simply <strong>de facto</strong> legal units, because they are the units that federal laws and regulations in fact use?</p>

<p><strong>Discussion</strong></p>

<p><strong>The U.S. and metric units in general</strong></p>

<p>The volt, the ampere, etc. are part of the SI system if units, and U.S. laws and regulations do have sections that deal with that system. But, as we will see, the mandate to actually use the SI units in general is rather weak.</p>

<p>In 15 U.S.C.<a href="https://uscode.house.gov/view.xhtml?req=granuleid%3AUSC-prelim-title15-chapter6&amp;saved=L3ByZWxpbUB0aXRsZTE1L2NoYXB0ZXI2L3N1YmNoYXB0ZXI1%7CZ3JhbnVsZWlkOlVTQy1wcmVsaW0tdGl0bGUxNS1jaGFwdGVyNi1zdWJjaGFwdGVyNQ%3D%3D%7C%7C%7C0%7Cfalse%7Cprelim&amp;edition=prelim" rel="nofollow noreferrer">Ch. 6—Weights and measures and standard time</a> there is the following:</p>

<blockquote>
  <p>§204. Metric system authorized</p>
  
  <p>It shall be lawful throughout the United States of America to employ the weights and measures of the metric system; and no contract or dealing, or pleading in any court, shall be deemed invalid or liable to objection because the weights or measures expressed or referred to therein are weights or measures of the metric system.</p>
  
  <p>§205. Metric system defined</p>
  
  <p>The metric system of measurement shall be defined as the International System of Units as established in 1960, and subsequently maintained, by the General Conference of Weights and Measures, <strong>and as interpreted or modified for the United States by the Secretary of Commerce.</strong></p>
</blockquote>

<p>Note that 15 U.S.C. 204—which has been on the books <a href="https://web.archive.org/web/20200608105604/https://govtrackus.s3.amazonaws.com/legislink/pdf/stat/14/STATUTE-14-Pg339.pdf" rel="nofollow noreferrer">since 1866</a>— only says that there can be no legal trouble arising from using the metric units; it doesn't require their use. </p>

<p>The most that the federal reulations require (<a href="https://www.govinfo.gov/content/pkg/CFR-2006-title15-vol3/pdf/CFR-2006-title15-vol3-sec1170-3.pdf" rel="nofollow noreferrer">15 CFR 1170.3</a>) is that</p>

<blockquote>
  <p>each  Federal  agency,  by  a  date  certain  and  to  the  extent  economically feasible by the end of the fiscal year 1992, use the metric system of measurement in its procurements, grants, and other business-related activities, except to the extent that such use is impractical or  is likely to cause significant inefficiencies or loss of markets to  United States firms, such as when foreign competitors are producting competing products in non-metric units. </p>
</blockquote>

<p>Obviously, it is fairly easy to conclude in most particular cases that such use would be 'impractical'. As a result, despite these regulations, the U.S. Government (not to mention U.S. society at large, which does not fall under the scope of this particular regulation) continues to use the U.S. customary units in a majority of areas of activity.</p>

<p>All this to say, U.S. regulations as they concern the SI system of units <em>in general</em> are a very weak foundation on which to base any sort of mandate for the use of SI units of electric measure in everyday activity. </p>

<p>Now, there used to be federal law that specifically addressed the units of electric measure: 15 U.S.C. 223 and 224 (see below). However, those sections were reapealed in 2007.</p>

<p>So my question is about whether there is now, following the 2007 repeal of 15 U.S.C. 223 and 224, any fedear law or regulation that explicitly singles out the volt, the ampere, etc. as legal units of electric measure.</p>

<p><strong>My <em>best guess</em> as far as what is the <em>current</em> legal status of the volt etc.</strong></p>

<p>On the one hand, I would say that the units of electrical measure are currently whatever the National Institute of Standards and Technology (NIST, the relevant agency of the Department of Commerce) says they are. This would be kind of like how the yard and the pound are what NIST says they are; see e.g <a href="https://web.archive.org/web/20200517202319/https://www.govinfo.gov/content/pkg/FR-1959-07-01/pdf/FR-1959-07-01.pdf" rel="nofollow noreferrer">here</a> (p.&nbsp;5348) and <a href="https://web.archive.org/web/20200518104910/https://www.govinfo.gov/content/pkg/FR-2019-10-17/pdf/2019-22414.pdf" rel="nofollow noreferrer">here</a> ("Deprecation of the United States (U.S.) Survey Foot"). Note that these are notices from the Federal Register. Therefore, if NIST had made any regulations about the volt and the ampere being <em>in general</em> the legal units of electric measure, I would also think that NIST would have published it in the Federal Register. However, so far, I haven't found anything.</p>

<p>On the the other hand, even if NIST hasn't laid down any such regulation, it probably doesn't matter in practice (which might be why it hasn't). The thing is, unlike with the units of e.g. length and mass, there is no realistic alternative to using the SI units of electric meausre: the volt, the ampere, and the rest of it. There are no 'U.S. cutomary units of electricity', unless they are exactly the SI units. Only in specialized applications does anyone use the older Gaussian units, and even then only some of them. (For example, to measure magnetic induction, much of industry still uses the gauss rather than tesla, which is the appropriate SI unit. I don't think <em>anyone</em> actually uses the Gaussian units for potential and current, the statvolt and statampere.) In short, to my knowledge, <em>everyone</em> in practice uses the volt, the ampere, and the ohm (including their versions with the metric prefixes, of course: the kilovolt, the milliamp, etc.). </p>

<p>Another consideration is that the standard electric units (the volt, the ampere, the ohm, etc.) are, by now, embedded in a mass of other regulation, concerning anything from fire safety (e.g. what kind of fuses and cables are required; here the voluntary <a href="https://en.wikipedia.org/wiki/National_Electrical_Code" rel="nofollow noreferrer">National Electrical Code</a> seems relevant) to lab certifications and electrical power-plant approval processes.</p>

<p><strong>My questions:</strong></p>

<p>Are my guesses correct? In particular, is it really true that, since 2007, there is no single place in U.S. laws and regulations (including e.g. notices in the Federal Register) that says that e.g. electric current is supposed to be measured in amps? <strong>More generally, what is the current <em>legal</em> situation with units of electric measure (the volt, the ampere, the ohm, etc.) in the United States?</strong></p>

<p>Also, what exactly did the lawmakers mean by 'repeal of redundant and obsolete authority' in the case of 15 U.S.C. 223 and 224?</p>

<p><strong>Another way to phrase my question</strong></p>

<p>Suppose the year is 2002, and a utility company decides to change all its documents, contracts, etc. so that everything is expressed in e.g. <a href="https://en.wikipedia.org/wiki/Statvolt" rel="nofollow noreferrer">statvolts</a> and statamps. In 2002, 15 U.S.C. 223 and 224 might have been interpreted as saying that this company can't do that,, and that a judge might order it to start using volts and amps. </p>

<p>What about now? If the company tries to do business in statvolts and statamps now, is there any federal regulation, presumably set by the Department of Commerce, that the company would be violating?</p>

<p>(Also, can one find out for sure if there is any such regulation?)</p>

<p><br><br><br>
<strong>Appendix: previous US laws</strong></p>

<p>On July 12, 1894, the US enacted <a href="https://www.loc.gov/law/help/statutes-at-large/53rd-congress/session-2/c53s2ch131.pdf" rel="nofollow noreferrer">An Act To define and establish the units of electrical measure</a> (28 Stat. 101 and 102), which became 15 U.S.C. 221 and 222. The act stated that </p>

<blockquote>
  <p>…from and after the passage of this Act the legal units of electrical measure in the United United States shall be as follows:</p>
  
  <p>First. The unit of resistance shall be what is known as the <strong>international ohm</strong>, which is substantially equal to one thousand million units of resistance of the centimeter-gram-second system of electro-magnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice fourteen and four thousand five hundred and twenty-one ten-thousandths grams in mass, of a constant cross-sectional area, and of the length of one hundred and six and three-tenths centimeters.</p>
  
  <p>Second. The unit of current shall be what is known as the <strong>international ampere</strong>, which is one-tenth of the unit of current of the centimeter-gram-second system…</p>
</blockquote>

<p>and so on. The act proceded to define several additional units: electrical potential (the international volt), charge (international coulomb), capacitance (international farad),  work (joule), power (watt), and inductance (henry). The prefix 'international' (as in, 'the international ohm') has to do with some complications that the definitions of units had to deal with at the time. These complications are not important for the present purposes, but can be read about <a href="https://en.wikipedia.org/wiki/International_System_of_Electrical_and_Magnetic_Units" rel="nofollow noreferrer">here</a>.</p>

<p>The previous act was repealed when, on July 21, 1950, the US enacted <a href="https://www.loc.gov/law/help/statutes-at-large/81st-congress/session-2/c81s2ch484.pdf" rel="nofollow noreferrer">An act to redefine the units and establish the standards of electrical and photometric measurements</a> (64 Stat. 370), which became 15 U.S.C. 223 and 224. The Act stated that</p>

<blockquote>
  <p>…from and after the date this Act is approved, the legal units of electrical and photometric measurement in the United States of America shall be those defined and established as provided in the following sections.</p>
  
  <p>SEC. 2. The unit of electrical resistance shall be the ohm, which is equal to one thousand million units of resistance of the centimeter-gram-second system of electromagnetic units.</p>
  
  <p>SEC. 3. The unit of electric current shall be the ampere …</p>
</blockquote>

<p>And so on. That became 15 U.S.C. 223, while the following became 15 U.S.C. 224:</p>

<blockquote>
  <p>It shall be the duty of the Secretary of Commerce to establish the values of the primary electric and photometric units in absolute measure, and the legal values for these units shall be those represented by or derived from, national reference standards maintained by the Department of Commerce.</p>
</blockquote>

<p>Here 'maintained by the Department of Commerce' in effect means 'maintained by the National Bureau of Standards', which was later renamed to the National Institute of Standards and Technology (NIST) and which is an agency of the Department of Commerce.</p>

<p>This Act was amended in 1963 to replace 'candle' by 'candela' (<a href="https://uscode.house.gov/statviewer.htm?volume=77&amp;page=299" rel="nofollow noreferrer">Pub. L. 88–165, Nov. 4, 1963, 77 Stat. 299</a>).</p>

<p>Sections 223 and 224 were part of U.S.C. until 2006 (see <a href="https://www.govinfo.gov/content/pkg/USCODE-2006-title15/pdf/USCODE-2006-title15-chap6-subchapV-sec221.pdf" rel="nofollow noreferrer">here</a> and <a href="https://www.govinfo.gov/content/pkg/USCODE-2006-title15/pdf/USCODE-2006-title15-chap6-subchapV-sec224.pdf" rel="nofollow noreferrer">here</a>). However, in 2007, they were repealed by the America COMPETES act, which became <a href="https://uscode.house.gov/statviewer.htm?volume=121&amp;page=598" rel="nofollow noreferrer">Pub. L. 110–69, title III, §3013(c)(2), Aug. 9, 2007, 121 Stat. 598</a> and which says the following:</p>

<blockquote>
  <p>SEC. 3570. METRIC SYSTEM DEFINED. </p>
  
  <p>The metric system of measurement shall be defined as the International System of Units as established in 1960, and subsequently maintained, by the General Conference of Weights and  Measures, and as interpreted or modified for the United States by the Secretary of Commerce.</p>
  
  <p>(2)  REPEAL OF REDUNDANT AND OBSOLETE AUTHORITY.— The Act of July 21, 1950, entitled,  ‘‘An  Act  To  redefine  the  units  and  establish  the  standards  of  electrical  and  photometric  measurements.’’  (15  U.S.C.  223  and  224)  is hereby repealed.</p>
</blockquote>

<p>As a result, the relevant part of U.S.C. looks <a href="https://www.govinfo.gov/content/pkg/USCODE-2018-title15/pdf/USCODE-2018-title15-chap6-subchapV-sec221.pdf" rel="nofollow noreferrer">like this</a>:</p>

<blockquote>
  <p>SUBCHAPTER  V—STANDARDS OF ELECTRICITY</p>
  
  <p><strong>§§ 221,  222.  Repealed.  July  21,  1950,  ch.  484,  § 13,64 Stat. 370</strong></p>
  
  <p>Sections, act July 12, 1894, ch. 131, §§ 1, 2, 28 Stat. 101,102, related to units of electrical measure.</p>
  
  <p><strong>§§ 223,  224.  Repealed.  Pub.  L.  110–69,  title  III,§ 3013(c)(2), Aug. 9, 2007, 121 Stat. 598</strong></p>
  
  <p>Section 223, acts July 21, 1950, ch. 484, §§ 1–11, 64 Stat.369;  Pub.  L.  88–165,  Nov.  4,  1963,  77  Stat.  299,  related  to units of electrical measure.</p>
  
  <p>Section 224, act July 21, 1950, ch. 484, § 12, 64 Stat. 370,related  to  establishment  of  values  of  primary  electricand  photometric  units  in  absolute  measure  and  legalvalues for those units.</p>
</blockquote>

<blockquote>
  <p>Is that really so, though? Is there, since 2007, no single place in U.S. regulations (including e.g. the Federal Register) that says that e.g. electric current is supposed to be measured in amps? More generally, what is the current legal situation with units of electric measure (the volt, the ampere, the ohm, etc.) in the United States?</p>
</blockquote>

<p>These units are authorized for use by <a href="https://www.law.cornell.edu/uscode/text/15/204" rel="nofollow noreferrer">15 USC 204</a>, quoted in the question.  The statute further authorizes the Secretary of Commerce to interpret or modify the standard, but it does not require it.  In the absence of any such interpretation or modification, the provisions of the standard are authorized as they are.</p>

<blockquote>
  <p>Also, what exactly did the lawmakers mean by 'repeal of redundant and obsolete authority' in the case of 15 U.S.C. 223 and 224?</p>
</blockquote>

<p>They meant that there was no need for those sections, which specifically authorized the use of certain metric-system measures, in light of the general authorization to use the entire metric system.</p>

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