Hugo Grotius, Father of International Law.  Portrait by Michiel Jansz. van Mierevelt, 1631 (via Wiki).

Litigators tend to get a bit skittish when treaty law creeps into lawsuits.  And with good reason– most American lawyers come up against treaties only very rarely, and their effects can really harm the unaware.  I promise you, in whatever practice area, sooner or later, some treaty or other doctrine of international law will have an effect on what they (you) do, and it’s critical to know where the landmines are buried.

All that said, let me bring the vaunted idea of a treaty down to the 1L level, because all you need to really know about treaties, you picked up in first year Contracts.  That’s all a treaty is: a contract.  Meeting of minds, offer, acceptance, consideration, breach, remedies, adhesion…  All that stuff plays into treaty analysis, because a treaty is just a contract.*  A special kind of contract.  See Foster v. Neilson, 27 U.S. 253, 314 (1829):

A treaty is in its nature a contract between two nations, not a legislative act. It does not generally effect, of itself, the object to be accomplished, especially so far as its operation is infra-territorial; but is carried into execution by the sovereign power of the respective parties to the instrument.

And remember the characterization of a contract as a sort of particularized law, enacted by the parties to govern a particular relationship.

Just about every treaty refers to its signatories as “Contracting States” or “High Contracting Parties”, so you don’t necessarily need Justice Story to illustrate the point.

That said, note the careful wording of the opinion (here’s where it gets a bit complicated).  A treaty in its nature is… not a legislative act.   But by virtue of the Supremacy Clause, it takes on the authority of a legislative act because it is ratified with the consent of the legislature (or at least half of it) and becomes supreme law.**  It thus overrides any lower authority in conflict with it.

Obviously, the best example in my world: the Hague Service Convention, which technically forces U.S. rules to give way to foreign law.

You read that correctly.  Foreign law overrides U.S. law.

Let’s say you’re suing a German defendant in federal court.  Due process requires that you serve by a means reasonably calculated to (1) put the defendant on notice and (2) provide the opportunity to defend.  FRCP 4(f) says serving by mail is okay if a treaty allows it, right?  And Article 10(a) of the Convention says mail is acceptable, right?

Well, not exactly.  They both defer to the other country’s viewpoint on the issue.  Rule 4(f)(2)(C)(ii) says mail service is okay*** if a treaty allows but doesn’t specify other means– and provided it isn’t prohibited by the foreign country’s law.  (See?  Even the FRCP defers to foreign law.)

But we don’t even need to analyze German law, because as it applies to Germany, the Hague Service Convention doesn’t allow it!

Article 10:  Provided the State of destination does not object…

Germany objects– as do China, Mexico, Switzerland, Korea, etc.– so Article 10, including the “postal channels” option in 10(a), is off the table.  A treaty thus allows a foreign country to override U.S. rules.  [That’s really gotta rub Roy Moore the wrong way!]

The power of this contract really is massive.

* Remember that you can have a contract without paper.  Even absent a written treaty, customary international law can still bind nations to a certain code of conduct.  Imagine customary law like you view usages… how have we done it in the past?  Course of performance, course of dealing, usage in trade… same concept, but applied differently.

** Not to get into tall weeds, but there are actually two types of treaty: those that come into effect by their own language upon ratification, and those that require implementing legislation.  The latter sort really does become a legislative act, requiring both chambers’ assent.

*** It’s usually a horrible idea– even if it’s legal.  And even in those rare cases where mail is the only viable option, it still must be done properly.