28 U.S.C. 2403(a) and State Court Litigation

One of my favorite statutes, 28 U.S.C. 2403(a), says that when a federal court is hearing a case in which the constitutionality of a federal statute is drawn into question, the court is supposed to notify the Attorney General if the United States is not already a party:

In any action, suit or proceeding in a court of the United States to which the United States or any agency, officer or employee thereof is not a party, wherein the constitutionality of any Act of Congress affecting the public interest is drawn in question, the court shall certify such fact to the Attorney General, and shall permit the United States to intervene for presentation of evidence, if evidence is otherwise admissible in the case, and for argument on the question of constitutionality. The United States shall, subject to the applicable provisions of law, have all the rights of a party and be subject to all liabilities of a party as to court costs to the extent necessary for a proper presentation of the facts and law relating to the question of constitutionality.

The purpose seems pretty clear and pretty sensible. A lot of direct challenges to a statute would already name the U.S. or a federal agent as a defendant, but a statute might be held unconstitutional in other cases, where the statute creates a private cause of action or a private defense. Given the way judicial precedent operates, Congress doesn’t want a statute struck down without somebody responsible to the federal government having a chance to defend the statute and make the best arguments for it, or maybe to advocate a limiting instruction to save the statute from invalidation. Plus letting the United States intervene as a party lets the United States appeal or seek certiorari if the statute is struck down. (Federal courts sometimes miss this requirement, as discussed briefly in Oklahoma ex rel Edmonson v. Pope.)

But I’ve been thinking lately about Garden State Equality v. Dow — the New Jersey case about civil unions and their interaction with federal law — and wondering: why doesn’t the statute apply in state courts, too? (If he reads the internet, it may well be that the Attorney General already knows about the Garden State litigation and New Jersey’s suggestion that federal agencies are applying federal law unconstitutionally, but the general point remains.)

The language above applies only to “a court of the United States,” and that term is separately defined only to include various federal courts. I would think there’s just as strong of a federal interest in intervening in state-court litigation, which the executive branch is even less likely to know about otherwise, and where state courts might sometimes be more hostile to federal interests.

Does the limitation stem from some kind of constitutional concerns about Congress’s power to regulate state procedure? (Cf. Anthony Bellia.) Am I wrong to think it would be a useful tool of executive branch litigation? Is there some other mechanism that makes it unnecessary?