The stakes could not be higher for Congress as President Trump tries to undermine its constitutional right and responsibility to oversee the executive branch.

The president has said he will refuse all subpoenas, has sued banks to stop them from providing information to Congress, has said the special counsel Robert Mueller should not testify and has sought to deny Congress access to the records of the former White House counsel, Don McGahn. At the same time, Attorney General William Barr is refusing to testify before the House Judiciary Committee if questioned by the panel’s lawyers, and Treasury Secretary Steven Mnuchin says he won’t give Congress the president’s tax returns despite a law giving the tax-writing committees access to any tax return.

The broad sweep of these efforts threatens the country’s history of accommodation between the two branches and the checks and balances that are the cornerstone of our democracy.

Congress is vested by the Constitution with oversight of the executive branch. The Supreme Court, moreover, has been explicit that Congress has broad power to seek information connected to a “legislative function” and to enforce its demands through its inherent contempt authority. This can include imprisoning someone who declines to comply with a subpoena.