Is that Constitutional, Torie asks, and then finds the below in the article:
"Vikram Amar, the dean of the University of Illinois College of Law, said that a patchwork of ballot access requirements in states that leave voters in different states with different choices in a national race could violate the Constitution. But he also said tax disclosure rules could stand if courts agree that states have wide latitude even in running presidential elections. Such a decision could also open the door for other requirements — such as a barring candidates such as Trump who have never held public office or politicians who have been in office for decades, Amar said."
The above is an understatement. I strongly suspect SCOTUS would just say no. It is adding qualifications for a federal office that are not in the Constitution, and go beyond merely ministerial matters.
The public square is going off the rails - yet again! It seems these days to be an almost daily occurrence. Where are my meds? 
Hmmm, I'm not so sure. The constitutional argument seems flimsy to me. The obvious analogue would be
U.S. Term Limits Inc. v. Thornton where SCOTUS struck down state attempts to impose term limits on members of congress even where the state framed it as a mere "ballot access restriction". The Court indeed ruled there that it amounted to unconstitutionally imposing a new requirement on the office beyond the age, residency, and citizenship requirements proscribed by the Constitution. But the obvious distinction would be that the law at issue in
Thornton absolutely prohibited fourth termed from being placed on the ballot for congress. Here, on the other hand, any candidate would be able to meet the requirement by disclosing their tax returns, so the law wouldn't actually prohibit anyone from seeking the office. It's more analogous to requiring petition signatures or filing papers within a deadline to gain access to the ballot.
I agree that a patchwork of different requirements for ballot access for presidential candidates across the country would be problematic, and I think a law requiring presidential candidates to disclose their tax returns would be silly, but there just isn't actually anything in the Constitution that requires every state to list the national Republican and Democratic nominees on their ballot. That being said, such a law might put a special burden on people who are, for instance, *sigh* under audit. So I think the better Constitutional argument would be a due process/ equal protection challenge assessed under the normal Anderson-Burdick test for ballot access restrictions, and I admit I don't know how that would turn out.
I also want to take this opportunity to reiterate what a tremendous coward I think Trump is for refusing to disclose his tax returns.
