WASHINGTON – A Trump administration proposal to limit protests at the White House and the National Mall, including by potentially charging fees for demonstrations, is meeting stiff resistance from civil rights groups who say the idea is unconstitutional.

The National Park Service is considering a plan to push back a security perimeter so that it would include most of the walkway north of the White House, a spot closed to traffic since 1995 that has become a regular venue for demonstrations. The proposal also floats the idea of allowing the agency to charge a fee for protests.

Though the ideas were proposed earlier this year, they are facing renewed attention given President Donald Trump's recent comments on protests following the confirmation of Supreme Court Associate Justice Brett Kavanaugh. Trump called the protesters "screamers" and claimed, without evidence, that they were funded by Democratic donors.

The proposals "harken back to the era in which the courts had to be called upon to protect the right to dissent in the nation’s capital," the American Civil Liberties Union wrote in a public comment letter to the National Park Service. "Many of the proposed amendments would be unconstitutional if adopted."

ACLU attorneys wrote that if a "cost recovery" fee for demonstrations had been in place in 1963, the historic March on Washington – in which the Rev. Martin Luther King, Jr., delivered his “I Have a Dream” speech – probably "couldn't have happened."

The National Park Service proposal did not include details about possible fees.

A spokesman for the service said the Occupy DC protest in McPherson Square in 2012 cost taxpayers $480,000. In that instance, protesters set up tents and stayed in the downtown Washington park for months.

"While we will always support the right to exercise their First Amendment rights of speech and assembly, we want to know the public’s views on whether this is an appropriate expenditure of National Park Service funds," NPS spokesman Brent Everitt said in statement.

Thousands of people have submitted public comments on the proposal, including more than 8,700 this week. The comment period closes Monday.

More:Secret Service tightens White House security on south side