President Trump’s unprecedented decision to revoke the security clearance of John Brennan, the former director of the Central Intelligence Agency — and his publicly stated intention to consider revoking clearances of a list of other administration critics — raises fundamental questions about national security, presidential authority and the First Amendment.

I believe the president has grossly abused his authority and violated Mr. Brennan’s First Amendment right to speak freely. The president’s actions are therefore unconstitutional and demand a response from Congress.

Senator Daniel Patrick Moynihan foresaw the risks of unconstrained presidential authority over classified information and security clearances. In 1997 he led a commission that recommended, among other things, that Congress enact a statutory basis for the system, to ensure that information was classified only for genuine national security reasons and to provide due process for those who were not granted a clearance or had their clearance revoked. Many of the recommendations were adopted, but Congress chose not to enact a statute.

Senator Moynihan could not have foreseen that a president would abuse his powers by revoking a clearance, with no process at all, solely because the individual was exercising his First Amendment right to speak freely about policy issues. And he would be horrified if, in addition, a president threatened to revoke clearances of those who oversaw an investigation of a foreign power’s interference in our elections, as President Trump recently said he might do in an interview with The Wall Street Journal.