Governor Andrew Cuomo, we gather from the news reports, is suddenly full of praise for President Trump’s leadership in respect of the coronavirus. It’s an encouraging turn, given Mr. Cuomo’s remarks Monday as he announced that New York, Connecticut, and New Jersey have agreed to limit crowds, including private parties, to no more than 50 persons, and to take other actions to slow the virus.

Mr. Cuomo’s press call Monday was just obnoxious. Also on the line were the governors of New Jersey and Connecticut. It’s a rare day that any governor, let alone three of them, wants the feds to run his state. Yet Mr. Cuomo started out by claiming that the federal government has “been behind on this crisis from day one.” The governors complained of “a lack of federal direction and nationwide standards.”

What Mr. Cuomo announced is that the three states “have agreed to a common set of rules that will pertain in all of our states.” Then he warned: “So don’t even think about going to a neighboring state because there’s going to be a different set of conditions,” Mr. Cuomo said. Later in a press conference, he elaborated on what was worrying him: “‘state shopping’ where residents of one state travel to another and vice versa.”

What strikes us about this imbroglio, if that’s what it was, is the agreement between the three states. It is, after all, a bright-line violation of the Constitution — namely of Article One, Section Ten. It’s the section that lists certain things that American states can never do. One of the things it ordains is that, absent the consent of Congress, no state shall enter “any agreement” with “another state.” It is un-American in the constitutional sense.

We understand that over the years, the Supreme Court has taken a somewhat flexible view. It allowed an agreement between Maine and New Hampshire to build a modest bridge. It once suggested it would be okay for, say, Virginia and Tennessee to drain a swamp in parts of both states. Congress and the Court, though, have jealously guarded the principle here. And it strikes us that Mr. Cuomo was way ahead of his skis.

Particularly because what seemed to bother him was the prospect that if he clamped down on the virus in New York his neighbors might take advantage of it. Mr. Cuomo could have regulated his state anyway its own constitution and legislature were prepared to permit. No need for him to have clumb up on his high horse against a Mr. Trump. If we were the Congress — a stretch, to be sure — we’d have written Mr. Cuomo a pass.

And we’d set aside the incident as unworthy of remark, save for the rush of big government into our lives in the name of defeating this virus. The right of Americans peaceably to assemble — which, aside from the agreements clause, is what is being abridged here, after all — is part of the same article of the Bill of Rights as, say, the right to free speech, religion exercise, or the use of printing equipment. Could Governor Cuomo have shut down the New York Times if, in his view, it were so infecting our politics as to be dangerous?

Not only that, but the amounts of money being created to combat the coronavirus are astounding. We remember, during the last trillion-dollar crisis, Chairman Bernanke telling CBS that the Fed could raise interest rates in 15 minutes if it had to. Ten years later, interest rates are close to zero. Just to be clear: We’re keeping our social distance, like everyone else, and are fully serious about it. All the more reason to keep the Constitution close.