The US constitution doesn't prescribe that any state use common law. Louisianan law is based on the Napoleonic laws.

But is the federal government supposed to use it?

Imagine that for some reason, defying any obstacle, Congress passes a law to just exchange common law for civil law, and either the president signs it or else Congress has two thirds in each house ready to override a veto. They prohibit judges from using binding precedent either horizontally or vertically.

It would certainly confuse a lot of people and be extremely annoying for hundreds of thousands of lawyers and companies and all sorts of people, but I can´t think of anything in the Constitution tying the US collectively to common law.

Actually, that the US doesn't use a civil law code is somewhat odd given that it started its revolution and constitutionalization in an era where countries in revolt did often change to some sort of law codes, like France and Latin America.

  • 2
    You are aware of the main differences between common and civil law? Like that precedent is much weaker in the civil law system, but it does exist, especially downward?
    – Trish
    Aug 26, 2023 at 8:55
  • I know that civil law does use persuasive precedent, and usually attempts constante jurisprudence, but no decision is itself binding on any other court. Aug 27, 2023 at 14:26
  • 1
    not exactly: if for example the BGH determines one outcome, then that is binding to all lower courts as the correct interpretation of the statute in Germany.
    – Trish
    Aug 27, 2023 at 14:56

5 Answers 5


Since common law is subordinate to statutory law, any common-law jurisdiction can eliminate any part of common law by enacting a statute. Many US states have done this with criminal law, for example, enacting a criminal code that explicitly abolishes all common-law crimes.

Congress could similarly enact a statute changing the role of precedent in the judicial system, for example, or eliminating any other aspects of common law that persist in the federal system since (as you note) the constitution has nothing to say about it.


This question has not been adjudicated nor has the scenario you envision been attempted.

However, see John Harrison, "The Power of Congress Over Rules of Precedent" (2000) 50 Duke L.J. 503. He concludes that

Congress has substantial authority to legislate concerning the rules of precedent in federal court. My conclusion, put briefly, is that Congress at least may adopt any norm of stare decisis that a court reasonably could recognize.


The first question is whether the federal courts’ norms of precedent are the kind of legal rule that is susceptible to alteration by ordinary legislation. My answer is yes. Most of them are federal common law, or as it was once called, general law, and at least one seems to be derived from a statute. That conclusion takes the argument only part of the way. Congressional action is valid only if it rests on an enumerated constitutional power, and Congress may not, in the form of legislation, invade the executive or judicial powers. The relevant enumerated power here comes from the Necessary and Proper Clause, under which Congress may pass laws that carry into execution the other two powers. Such a congressional authority poses no threat to the separation of powers, or at least no more of a threat than the necessary and proper power inevitably does. That threat might be serious were Congress empowered to legislate with an eye to determining the doctrines according to which the courts decide cases. The necessary and proper power, however, authorizes legislation that is based on systemic considerations that are divorced from particular doctrinal results and hence would not enable Congress to control outcomes in areas where it may not legislate the substantive rule.

Recognize, though, that the argument that it is within Congress's power to substantially change the rules of precedent so as to move the federal system towards a more civilian tradition is itself based in common law reasoning. A Court called upon to adjudicate the propriety of such a statute would be put in the position of deciding whether this change to treatment of precedent is permissible, but likely would use the existing paradigm (rather than the new paradigm) to determine the answer.

Also recognize that a wholesale transition from a common law tradition to a civilian tradition would not and could not happen at the insistence of Congress. Congress could only affect certain aspects such as the rules of precedent described above. A full transition would require changing traditions, modes of thought and reasoning, respect for academic sources and doctrine, and the installation of true civilian Codes, not simply wide-sweeping statutes.


There is no structural requirement in federal law requiring courts to recognize precedent, however the proposal to "exchange common law for civil law" is hopelessly vague (we don't actually have "common law" in the US, we have a mixed system that is becoming increasingly statutory). Civil law systems are not completely devoid of the concept of precedent, where precedent is influential but not binding.

Under Article III Congress can establish – and disestablish – inferior courts, and has well-known power to make laws. This includes numerous law regarding how laws are to be interpreted (whence the numerous laws defining words "for the purpose of this section/chapter/title"), and numerous provisions in Title 28 telling the courts how to do their business. Even under English common law, the courts understand that their function is to interpret the laws passed by the legislature. A concrete proposal to limit the power of courts to "make law", and limit court power to just "applying law" would be possible, but not trivial to draft.


Yes, it is

If Congress attempted such a change, the Supreme Court would almost certainly strike it down as beyond their power. That’s because it would fundamentally change the functions of the Supreme Court - and Congress can’t do that. It could, theoretically be done through a Constitutional amendment, but why?

And we have a precedent.

In , the High Court was ask to rule as legally invalid, the basic assumption that led to the passing of the Australian Constitution Act by the UK Parliament - that the land was Terra Nullius or nobody’s land.

It’s a long-standing tenet of international law that when the sovereignty of land changes, if the land is unoccupied, it becomes subject to the law of the new owner, but if it was already occupied, the existing legal system continues. That’s why Louisiana has civil law, it was French territory before it was US territory. It has French law (substantially modified) because the French treated it as Terra Nullius when they occupied it; just like the English and later the Americans treated the rest of the US as Terra Nullius - so the US is built on the same legal mistake as Australia because there were, in fact, people and legal systems already present.

Incidentally, Florida doesn’t have civil law because it was Spanish territory but unoccupied and so didn’t have Spanish law (notwithstanding the many indigenous people living there).

The High Court decided that it didn’t have the legal power to render a judgement that would make itself a nullity. The US Supreme Court would embrace the precedent.

Now, that said, the common law of the US (and most other common law jurisdictions) is very heavily codified in a way that would be very alien to jurists of the 18th century. That looks a lot like civil law.

At the same time, Europe’s law is more guided by precedent than it was then. That looks a lot like common law.

  • Why would not the Supremacy Clause grant legislatively-passed statutes priority over any judicial rulings other than those which are compelled by the Constitution or treaties? Such rulings are not listed anywhere in the priority list.
    – supercat
    Aug 27, 2023 at 20:13
  • 2
    The Australia case is distinguished because there it was the court that would have made the change, not the legislative branch.
    – D M
    Aug 28, 2023 at 2:25
  • @DM no, the court made a decision on the interpretation of the legislation as would the US court. Legislation that fundamentally changes how the government operates is clearly unconstitutional.
    – Dale M
    Aug 28, 2023 at 10:24
  • @DaleM What legislation were they interpreting that purported to fundamentally change the way the government operates? The only law I see mentioned is the Australia Constitution Act itself, which is like the one thing that cannot possibly be unconstitutional. That was an act of the UK Parliament that created the Australia constitution. (The UK has no constitution, as I understand it.) Or is there other legislation you're referring to?
    – D M
    Aug 28, 2023 at 11:16
  • 1
    @DM changing the basis of the law doesn’t affect most cases, it affects all cases.
    – Dale M
    Aug 29, 2023 at 2:52

Imagine that for some reason, defying any obstacle, Congress passes a law to just exchange common law for civil law (...)

"Common law" or "civil law" is not some sort of clear-cut statute that can be established or revoked by signing the appropriate legal instrument.

[Imagine that] they prohibit judges from using binding precedent either horizontally or vertically.

The federal Congress (or state houses) could certainly pass a statute requiring that (federal or state) courts rule according to criteria X, Y and Z, and explicitly require additional motivation beyond precedent. That would throw the whole system into chaos, but it could in theory be done.

Arguably, there might be constitutional issues. Article III or the federal US Constitution says that the Supreme Court "shall have appellate Jurisdiction, both as to Law and Fact, with such Exceptions, and under such Regulations as the Congress shall make". One might wonder if it is really "appelate jurisdiction" if it does not set precedent. (But all that could be bypassed by a constitutional amendment anyway.)

As an aside, and as mentioned in the comments under the original post, that would be widely out of line of how civil law systems work. Precedent is binding vertically, and in most civil-law jurisdictions repeated precedent (jurisprudence constante) is binding horizontally.

Actually, that the US doesn't use a civil law code is somewhat odd given that it started its revolution and constitutionalization in an era where countries in revolt did often change to some sort of law codes, like France and Latin America.

I think there are a few historical misconceptions in that sentence.

The basic premise of a civil law code is rooted in the Enlightement ideas that such a code should be based on a rational fundation of law principles and replace a hodgepodge of local customs and rulings.

It has no a priori affinity with constitutionalization; as Wikipedia shows, civil law codes were promulgated in the late 18th century in various German-speaking states, before the French invasion(s). Those countries were absolute monarchies at the time and nowhere close constitutional government.

In fact, so was France in 1804, when the civil code was promulgated. At that time, Napoleon was firmly in control and operated under a very lightweight constitution that had done away with the constraints on executive power given in the declaration of the rights of man and of the citizen (French equivalent of the US Bill of Rights). It was not a divine-right-of-kings monarchy, but it was still a brutal autocracy.

The Napoleonic code was more successful, not because it was revolutionary and copied by other revolutionary countries, but because Napoleon exported it by force across continental Europe, and as a consequence to its colonies (including most of Latin America). That brutal change did not happen in the UK (which was never under French domination) or its colonies (notably non-Quebec Canada).

The US were never invaded by Napoleon either and therefore did not adopt the Napoleonic code. (Whether the US could have produced their own civil code at some point during or after the independence war with the UK is a fun bit of alternate history, but they did not.)

I would argue that the difference between "civil law systems" and "common law systems" is not one of philosophy, where different legal thinkers decided to establish whole sets of law based on different basic principles. It is rather one of history, where many civil law systems look the same because they were forcibly aligned in the early 19th century, and many common law systems look the same because they were either the UK or colonies of the UK.

Rather than "civil law systems" and "common law systems", they could be called "1804-Napoleonic-code-derived systems" and "Englo-British-medieval-law-derived systems". The distance in legal philosophies between current-day France and UK in probably smaller than the distance between the 1792 Prussian Allgemeines Landrecht für die Preussischen Staaten and the 1804 French Code Civil.

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