The problem with this argument is, as Judge Tatel writes, no case law supports the dissent. What the Supreme Courts decisions actually say is, Congresss authority ... to require pertinent disclosures in aid of its own constitutional power is not abridged merely because the information sought to be elicited may also be of use in criminal prosecutions.
Tatel also rejects Trumps second argument, that financial disclosure laws cannot be applied to the present. As the Supreme Court explained in Nixon v. Administrator of General Services (1977), in determining whether [a law] disrupts the proper balance between the coordinate branches, the proper inquiry focuses on the extent to which it prevents the Executive Branch from accomplishing its constitutionally assigned functions. Thus, a presidential financial disclosure law would only be unconstitutional if it were somehow so onerous as to prevent the president from fulfilling his constitutionally assigned functions.
In Tatels words, we have no basis for concluding that complying with financial disclosure laws would in any way disrupt those functions.
Now that the DC Circuit has ruled, however, Trump will almost certainly seek a stay of this decision from the Supreme Court. Both Tatel and the other judge in the majority, Judge Patricia Millett, are center-left judges who are well to the left of the current Supreme Court. Judge Rao, meanwhile, is a former law clerk to ultraconservative Justice Clarence Thomas, and her past writings suggest that she is well to the right of the median justice.
We do not yet know whether judges like Chief Justice John Roberts will follow existing precedents that support this investigation. Should Trump receive an emergency stay from the Supreme Court, that could hand him a victory even if he ultimately loses this case on the merits as the Supreme Court may not decide the case for months or even years.
The fight over whether Trump is immune to investigation, in other words, just entered its end game. The Supreme Court will have to show its hand very soon and that will tell us whether existing law applies to this president.