Arguably, there is a smidgen of dramatic irony here. Part one of the four-part test that Judge Marcus referenced is that the federal spending program (and condition) must promote "the general welfare" of the United States. But then the Court, in a footnote, goes on to explain that whether a spending program promotes the general welfare may well be a purely political question, not meet for judicial review. Specifically, Chief Justice Rehnquist wrote thus:
The level of deference to the congressional decision is such that the Court has more recently questioned whether "general welfare" is a judicially enforceable restriction at all. See Buckley v. Valeo, 424 U.S. 1, 90-91 (1976) (per curiam).In other words, the very passage that Judge Marcus himself cited shows how a requirement might be a part of a constitutional test spelled out by the Supreme Court in one of its opinions, and yet not be something that is generally appropriate for federal courts to enforce.
So, with all due respect to Judge Marcus, General Katyal's statement may be perfectly understandable: the coercion test (just like the "general welfare" test) may be a requirement under the Constitution, but one that is (barring extraordinary circumstances) to be enforced through the political process, rather than the courts.