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Volokh Conspiracy

New Draft Article: "Cross-Enforcement of the Fourth Amendment"

The surprising uncertainty when the Fourth Amendment meets federalism.


I recently posted a draft of a new article, Cross-Enforcement of the Fourth Amendment, forthcoming in the Harvard Law Review. Here's the opening:

Imagine you are a state police officer in a state that has decriminalized marijuana possession. You pull over a car for speeding, and you smell marijuana coming from inside the car. Marijuana possession is legal under state law but remains a federal offense. Can you search the car for evidence of the federal crime even though you are a state officer?

Next imagine you are a federal immigration agent driving on a state highway. You spot a van that you have a hunch contains undocumented immigrants. You lack sufficient cause to stop the van to investigate an immigration offense, but you notice that the van is speeding in violation of state traffic law. Can you pull over the van for speeding even though you are a federal agent?

Here's the abstract:

This Article considers whether government agents can conduct searches or seizures to enforce a different government's law. For example, can federal officers make stops based on state traffic violations? Can state police search for evidence of federal immigration crimes? Lower courts are deeply divided on the answers. The Supreme Court's decisions offer little useful guidance because they rest on doctrinal assumptions that the Court has since squarely rejected. The answer to a fundamental question of Fourth Amendment law – who can enforce what law – is remarkably unclear.

After surveying current law and constitutional history, the Article offers a normative proposal to answer this question. Drawing on principles of agency law, it proposes that each government should have the power to control who can enforce its criminal laws. Only those authorized to act as agents of a sovereign should enjoy the privilege of searching and seizing to enforce its laws. The difficult question is identifying authorization: Questions of constitutional structure suggest different defaults for enforcement of federal and state law. Outside the Fourth Amendment, governments can enact statutes that limit how their own officers enforce other laws. The scope of federal power to limit federal enforcement of state law by statute should be broader, however, than the scope of state power to limit state enforcement of federal law.

Comments are particularly welcome in the next week or two, as the editing process has begun and I'll have a chance to make major revisions in the short term that may be harder to make in the longer term. You can send comments to me at okerr [at]

Some readers may remember my post from last May at the old WaPo site about the Second Circuit briefs filed in Marsh v. United States, a 1928 case decided by Learned Hand. At the time, I noted my "mild obsession" with Marsh because of its relevance to my work-in-progress on cross-enforcement. Readers of the new draft will see why: Marsh ends up being an important case.