Better late than never, although this is pretty darned late for the modern news cycle. More than two weeks ago, five Senate Democrats threatened to pack the Supreme Court if they chose to hear a gun-control challenge out of New York. Sheldon Whitehouse wrote in an amicus brief that New York had mooted the case by repealing the law, and that taking the case anyway would show a bias that could only be corrected by having the top court “restructured in order to reduce the influence of politics,” in one of the more self-unaware declarations made by a leading politician.

Senate Republicans finally responded to this nice court ya got dere threat. In a letter to the court clerk, Mitch McConnell and all of the other 52 Senate Republicans told the court that their independence as a separate but equal branch was on the line:

All 53 Republicans in the Senate urged the Supreme Court on Thursday not to be “cowed” by a brief from a handful of Democratic senators that warned that the court risks its impartial reputation if it continues to hear a gun case that the Democrats consider moot.

In a letter to the court’s clerk, the Republicans said the brief filed by Sen. Sheldon Whitehouse (D-R.I.) and four other Democrats “openly threatened this court with political retribution if it failed to dismiss the petition as moot.”

The justices “must not be cowed by the threats of opportunistic politicians,” said the letter, drafted by Senate Majority Leader Mitch McConnell (R-Ky.).

McConnell put this in stark terms as a constitutional affront:

Why send a letter rather than an amicus brief opposing the one from Whitehouse et al? McConnell writes that “we take no position” on the case in question, which makes this outside the scope of an amicus brief. However, McConnell declares, “judicial independence is not negotiable,” and that Senate Republicans will “brook no threats to this fundamental precept of our constitutional structure.”

He then exhorts the Supreme Court to judge the cert application on its merits, not on the politics of a few. “They should rule in this case only as the law dictates,” McConnell says of the justices, and pledges to make sure politicians don’t threaten their independence in the future:

Well, it’s not as if the idea of court-packing hasn’t gotten some play on the Right too, especially in relation to overturning Roe v Wade. Democrats’ rhetoric on court packing has encouraged some of that in response. However, as far as I know, none of that has made it into an amicus brief of any kind, let alone from members of Congress with the theoretical authority to try it. That crosses a Rubicon in terms of judicial independence, as McConnell notes. Belatedly, anyway.

One has to wonder whether the Whitehouse et al amicus might end up backfiring. All it takes is four members of the court to grant cert. New York’s attempt to kill this appeal by repealing the law still leaves some room for interpretation on enforcement but would otherwise have let the court off from a contentious case. Now, however, some justices might be inclined to grant cert just to demonstrate their independence from Congress — and to ensure that such bullying doesn’t continue in the future.