Is there one body of common law?
<p>I'm a bit confused by the usage of the phrase "common law" on this site. The Wikipedia <a href="https://en.wikipedia.org/wiki/Common_law" rel="nofollow noreferrer">article</a> initially describes it as an abstract concept. The first paragraph reads:</p>

<blockquote>
  <p>Common law (also known as case law or precedent) is law developed by
  judges through decisions of courts and similar tribunals that decide
  individual cases, as opposed to statutes adopted through the
  legislative process or regulations issued by the executive branch.</p>
</blockquote>

<p>Later on, the phrase also seems to refer to a specific body of English law established by court precedent:</p>

<blockquote>
  <p>Common law originated during the Middle Ages in England,[7] and from
  there was propagated to the colonies of the British Empire [..]</p>
</blockquote>

<p>This is more consistent with what I'm seeing on this site where specific laws are being cited as part of common law. So my understanding is that the phrase "common law" can refer to either the concept of laws established by court precedent or it can refer to a specific body of laws that have been established that way.</p>

<p>What confuses me now is the relationship between common law in different countries. I usually see the phrase being used here simply as "common law" without qualification such as "U.K. common law" or "Virginia common law".</p>

<p>Should I just be inferring that from context? Is there a single body of "common law"? Are there distinct bodies of "U.K. common law" and "U.S. common law" for example? If so, how are they related? Do judges in common law countries cite court decisions in other common law countries?</p>

<blockquote>
  <p>So my understanding is that the phrase "common law" can refer to either the concept of laws established by court precedent or it can refer to a specific body of laws that have been established that way.</p>
</blockquote>

<p>Yes.</p>

<blockquote>
  <p>Should I just be inferring that from context?</p>
</blockquote>

<p>Yes.</p>

<blockquote>
  <p>Is there a single body of "common law"?</p>
</blockquote>

<p>No.</p>

<blockquote>
  <p>Are there distinct bodies of "U.K. common law" and "U.S. common law" for example?</p>
</blockquote>

<p>Yes, furthermore there is different common law in England/Wales, Northern Ireland &amp; Scotland and each state of the US. Further, Scotland and Louisiana are not straightforward common law jurisdictions but rather a blend of common and civil law.</p>

<blockquote>
  <p>If so, how are they related?</p>
</blockquote>

<p>They are related in that they all:</p>

<ul>
<li>have a common source, middle English common law </li>
<li>evolve in the same way - judges interpreting the current common law and the statutes of the legislature </li>
<li>follow an appeals system through higher levels of courts. </li>
</ul>

<p>They do not all go in the same direction though.</p>

<blockquote>
  <p>Do judges in common law countries cite court decisions in other common law countries?</p>
</blockquote>

<p>Sometimes; it depends on the "distance" of the other jurisdiction. </p>

<p>A judge in New South Wales is quite likely to consider how judges in Queensland and Victoria have considered similar laws, less likely to look at the UK and Canada and extremely unlikely to look at the USA. </p>

<p>This has a lot to do with how far back it is since the "last common ancestor" of the law; the longer the corpus of law has been separated the more likely that the principles have diverged, partly this is cultural drift but mostly this is differences in statutes that actively modify the common law. Usually, jurisdictions within the same country are quite close to each other; partly due to common culture but often because of a genuine effort to "harmonise" laws across borders.</p>

<p>There are occasions, however, where legislatures "steal" laws from other jurisdictions, in which case they often look to each other for early development of common law on those laws. For example, the Alberta (Canada) <a href="http://www.qp.alberta.ca/documents/Acts/b07.pdf" rel="nofollow noreferrer">Builder's Lien Act 2000</a> and the NSW (Australia) <a href="http://www.austlii.edu.au/au/legis/nsw/consol_act/bacisopa1999606/" rel="nofollow noreferrer">Building and Construction Industry Security of Payment Act 1999</a> both address the same "wrong" and both had a common and parallel genesis pre-enactment; early cases in each jurisdiction were watched by the other.</p>

<p>Common law is based on the system of law established in England following the Norman Conquest in 1066.</p>

<p>Its principle was simple: that <strong>like cases should be treated alike</strong>. This differed from the prior laws, which varied between the different local courts, and in doing this, the kings (who, in the beginning, were the ones who <em>held</em> court) avoided arbitrariness. A bonus of this was that the king's decisions were binding upon all Englishmen.</p>

<p>Over time, a body of royal rulings built up, and this became the common law principles as we know it today. All common law systems that exist today are descendants of that medieval system, and so <em>often</em>, but not always, principles that apply in one common law country will apply in another.</p>

<p>The answers here that refer to common law in general do only that - refer to it <em>in general</em>.</p>

<p>Judges in common law jurisdictions will very often cite cases in other jurisdictions <em>when dealing with a novelty</em>. That is, if the case before them is the first in their jurisdiction, judges will refer to other common law countries for guidance.</p>

<p>Perhaps the most famous Australian example of this is the <em>Mabo v Queensland (No.2)</em> [1992] HCA 23, commonly known simply as the <strong>Mabo</strong> case, where the High Court of Australia overturned the principle of <em>terra nullius</em>. In the course of their judgment, they considered cases from:</p>

<ul>
<li>the New Zealand High Court</li>
<li>the UK Privy Council</li>
<li>the United States Supreme Court</li>
</ul>

<p>However, in general, they will look to cases considered by the same court and superior courts, before examining cases in other jurisdictions - this applies between different states, as well as between different countries. The reason for this is fairly straightforward, too: a superior court ruling would overturn a decision by the judge, and so carries more weight.</p>

<p>So, is there a single body of common law? There is, and there isn't. Judges in common law jurisdictions can, and do, refer to rulings in other jurisdictions. Whether they will apply those rulings depends on a number of things, but primarily on whether the <em>material facts</em> of the case before them are the same as those of the case being considered. Also, the attitudes of a particular court towards the application of foreign cases in domestic ones plays an important role - the US Supreme Court has been known to be particularly hostile to considering foreign cases, especially in relation to constitutional matters.</p>

<p>Keep in mind that court systems are generally organized into tree structures. If you look at the US federal system, there are district courts organized into circuits. The circuits are supposed to ensure uniformity (common law) among the district court beneath them. The U.S. Supreme Court is supposed to ensure uniformity among the circuits. </p>

<p>There is no one that ensures uniformity amount the various state courts or national court systems. There are distinct differences among the law of states and nations (and even among the U.S. circuits).</p>

<blockquote>
  <p>Is there a single body of "common law"? </p>
</blockquote>

<p>No.</p>

<blockquote>
  <p>Are there distinct bodies of "U.K. common law" and "U.S. common law" for example? </p>
</blockquote>

<p>Yes. And distinct law among the states.</p>

<blockquote>
  <p>If so, how are they related? Do judges in common law countries cite court decisions in other common law countries?</p>
</blockquote>

<p>Under the common law system, opinions from courts above form binding precedent. All other opinions form a body of other authority. </p>

<p>Common law countries frequently cite each other. For example, there are post independence UK precedents that are firmly established in American law. Here is an example of a Michigan Supreme Court opinion citing UK case law that it has adopted:</p>

<p><a href="https://scholar.google.com/scholar_case?case=13899490105769493329" rel="nofollow noreferrer">https://scholar.google.com/scholar_case?case=13899490105769493329</a></p>

<p>The courts of various nations frequently tend to cite each other when they interpret treaties, for example, treaties governing child custody. They also cite each other when another jurisdiction's law apply. E.g.,</p>

<ul>
<li>A contract case filed in an Australian court where the contract says NY Law applies.</li>
<li>A personal injury tort case filed in a NY court where the injury occurred in Australia (and Australian law applies).</li>
</ul>

united-states united-kingdom canada common-law australia