U.S. Code and the Supremacy Clause
<p>The  <a href="https://www.law.cornell.edu/uscode/text/18/1111" rel="nofollow noreferrer">18 U.S. Code § 1111</a> punished first degree murder by death</p>
<blockquote>
<p>Whoever is guilty of murder in the first degree shall be punished by death or by imprisonment for life;</p>
<p>Whoever is guilty of murder in the second degree, shall be imprisoned for any term of years or for life.</p>
</blockquote>
<p>The US code is a federal law, isn't it?</p>
<p>Now <a href="https://en.wikipedia.org/wiki/Supremacy_Clause" rel="nofollow noreferrer">Article VI, Clause 2</a> of the US Constitution, the &quot;Supremacy Clause&quot;, says that</p>
<blockquote>
<p>[...] the Laws of the United States [...] shall be the supreme Law of the Land [...] and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.</p>
</blockquote>
<p>This should imply that every state of the land should punish murder by death, no? How there can be States without death penalty?</p>

<p>While the point made by user6726 is not wrong with respect to this particular statute, it doesn't address a more basic point about how the supremacy clause works.</p>

<p>Federal criminal laws govern punishments for federal crimes in the federal criminal justice system.</p>

<p>Federal prosecutors bringing federal criminal charges against criminal defendants in the federal criminal justice system can and do secure death penalty sentences against criminal defendants in states where there is no state death penalty. </p>

<p>One recent case where that happened was the Boston Marathon bombing case where <a href="https://www.nytimes.com/2015/05/16/us/dzhokhar-tsarnaev-death-sentence.html?mcubz=1&amp;_r=0" rel="noreferrer">a defendant was sentenced to death in federal court</a> for the crime for violation of a federal criminal statute, despite the fact that Massachusetts has no death penalty of its own.</p>

<p>This is not a supremacy clause issue. No state law had to be changed or invalidated because of the existence of the federal law. States law governs how the state criminal justice system works, not the federal criminal justice system.</p>

<p>When we say that a state has abolished the death penalty, we mean that it has abolished it in the state criminal justice system. This doesn't absolutely foreclose the possibility that the death penalty will be imposed in that state on federal charges, although it does make it far less likely that the death penalty will be imposed.</p>

<p>Partially, this is because "blue collar" crime is handled by the states. Partially, this is because out of comity and a concern that juries in states without a death penalty are less likely to vote for a capital sentence, federal prosecutors are less likely to seek the death penalty in a state without capital punishment than in a state with capital punishment.</p>

<p>For example, there are <a href="https://deathpenaltyinfo.org/death-row-inmates-state-and-size-death-row-year?scid=9&amp;did=188" rel="noreferrer">2,902 people on death row as of 2016</a>, in the U.S. Almost 98% of death penalty convictions that have not yet been carried out were obtained in state courts. Only, 62 involve civilian death penalties imposed in federal courts (<a href="https://deathpenaltyinfo.org/federal-death-row-prisoners#list" rel="noreferrer">mostly in states that have the death penalty</a>) and another 6 involve death penalties imposed in military courts (<a href="https://en.wikipedia.org/wiki/List_of_death_row_inmates_in_the_United_States#United_States_military" rel="noreferrer">mostly in states that allow the death penalty or abroad</a>). All of the other cases arose in state courts.</p>

<p>The key is "jurisdiction". The law says "Within the <a href="https://www.law.cornell.edu/uscode/text/18/7" rel="nofollow noreferrer">special maritime and territorial jurisdiction</a> of the United States...". For instance, a murder in a national park is within the special maritime and territorial jurisdiction of the United states, but my backyard is not, rather it is within the jurisdiction of Washington State. "Special maritime and territorial jurisdiction" is a technical concept defined in 18 USC 7.</p>

<p>The indictment for <a href="https://www.justice.gov/iso/opa/resources/378201362714364690711.pdf" rel="nofollow noreferrer">Dzhokhar Tsarnaev</a> lists numerous federal crimes that he was charged with: <a href="https://www.law.cornell.edu/uscode/text/18/2332a" rel="nofollow noreferrer">18 USC 2322a(a)(2)</a> – weapons of mass destruction resulting in death; aiding and abetting same; use of firearms in same (<a href="https://www.law.cornell.edu/uscode/text/18/924" rel="nofollow noreferrer">18 USC 924(c)</a>; <a href="https://www.law.cornell.edu/uscode/text/18/2332f" rel="nofollow noreferrer">18 USC 2332f</a> – public bombing and related charges. In the first WMD charge, reference is made to interstate and foreign commerce and use of the mail, whereby this becomes a matter of concern at the federal level; <a href="https://www.law.cornell.edu/uscode/text/18/part-I/chapter-44" rel="nofollow noreferrer">firearms</a> are in general a matter of federal concern. In fact there are federal versions for quite a number of state crimes (e.g. controlled substances), and there isn't a bright legal line as to when federal charges vs. state charges will be pursued: typically, one prosecutor will defer to the other. However, as in the Rodney King beating, acquittal on state charges does not preclude later conviction on federal charges.</p>

united-states criminal-law constitutional-law us-constitution federalism