Federal Judge Tosses President Trump's Tax Return Lawsuit

President Trump filed to prevent New York prosecutors from accessing his tax returns. A judge rejected his claim of presidential immunity. Trump's legal team sued Mazars USA and DA Cyrus Vance, who subpoenaed eight years of tax returns. The DA is investigating the Trump Organization and payments to Stormy Daniels. Trump's attorneys argue the lawsuit addresses constitutional issues, and they have appealed the ruling.

What was the purpose of the DA's subpoena regarding President Trump's tax returns?

What significant constitutional issues did Trump's attorneys claim were at stake in the lawsuit?