Eight organizations have joined forces against a National Park Service proposal that would require activists to pay the government back for the cost of protests and limit where in Washington demonstrators can gather.

In its first collective act, the coalition submitted a letter Monday to members of Congress, urging them to push the acting director of the Park Service to halt attempts to change how the agency handles demonstrations. It is the latest push by civil rights groups and activist organizations to scuttle the Park Service’s proposal.

“Our organizations do not agree on all issues, but one principle we unreservedly support is our right to gather together to express ourselves,” the letter said. “The quintessential locations for these expressive gatherings in the United States are the National Mall and the public spaces surrounding the White House. . . . We are very concerned that, should these rules go into effect, they will chill speech and harm our national discourse.”

The group is led by the American Civil Liberties Union and comprised of organizations that include the left-leaning Public Citizen and the NAACP, as well as the conservative Charles Koch Institute and the March for Life Education and Defense Fund.

Dan Smith, the acting head of the Park Service, is scheduled to sit before the House Natural Resources Committee on Wednesday to discuss “the spending priorities and mission of the National Park Service.” Coalition members hope lawmakers will use the time to grill Smith on the viability and consequences of changing protest rules.

“We’re aware that the Park Service is ostensibly still going through public comments and making their decision on whether to implement these rules, and we wanted to make the point that we have our eye on them, and the best thing that could happen is for the National Park Service to withdraw them altogether,” said Kate Ruane, senior legislative counsel for the ACLU. Smith “has the authority now to approve [the proposals] if they come before him, and he also has the authority to withdraw them completely.”

A Park Service spokesman said the agency didn’t immediately have a comment Monday on the coalition’s letter.

Though the Park Service outlined more than a dozen changes in its August announcement to how the agency facilitates protests, the coalition zeroed in on three proposals it said were “particularly troubling.”

The first is whether the Park Service should explore charging protest organizers additional fees for permitted demonstrations, vigils and rallies, such as the costs of supporting and securing the event — charges that could include the cost of additional police officers called in for large-scale demonstrations.

The coalition also opposes a Park Service proposal that would close off a significant portion of the sidewalk outside the White House, where protesters routinely gather to picket and air grievances.

“The ability to gather and speak freely in the public square is such a core component of our First Amendment rights,” said Sarah Ruger, director of free expression for the libertarian Charles Koch Institute. “Any vanguard to defend free speech should be a diverse one and an apolitical one. Having such a diverse coalition of groups come together should send an unequivocal signal that the right to speak is not a right of interest to any one party or faction, but the interest of every American.”

The group’s third point of opposition centers on a proposal that coalition members said would stifle spontaneous demonstrations. Under the change, the Park Service would allow spur-of-the-moment demonstrations only if the agency has the resources and personnel readily available — rather than its current charge to make such resources available.

“One of the critical things for free speech rights is being able to speak now,” Ruane said. “If something happens — a tragedy happens and people converge in front of the White House holding candles to hold a prayer vigil — if there is concern that doing that would be in violation of the law, is it possible that spontaneous gathering wouldn’t happen?”

Park Service officials have said the agency’s limited resources have made facilitating protests difficult as the frequency and size of demonstrations have grown in recent years. But the idea of being asked to repay costs has alarmed activists, who said the charges would probably limit large-scale demonstrations to a select few groups that could afford to incur the costs.

Demonstration organizers aren’t required to pay for a permit to host a rally in the District, according to Park Service policy. There are other costs protesters do cover, including on-site emergency medics, trash cleanup and portable toilets.

Special events that aren’t deemed an exercise of free speech — such as concerts, weddings and festivals — are required to reimburse the Park Service for the agency’s time and resources.

The agency doesn’t track how much it spends to support First Amendment demonstrations, but spokesman Mike Litterst has said that, on average, processing permits alone costs the Park Service about $700,000 annually in staff time, with the number of permitted protests in Washington ballooning to about 750 per year.

The agency has increasingly found itself pulling from emergency funds to cover the cost of security, permit processing and cleanup, Litterst said.

In brainstorming ways to recoup costs, the Park Service in August opened the question to public comment of whether protesters should repay certain security and support costs. It received more than 140,000 replies in 60 days, but hasn’t issued a final ruling.

In an attempt to secure a stronger rebuke of the proposal, the ACLU asked senators last year to raise the issue with David Vela, President Trump’s pick to lead the Park Service. Vela refused to say whether he would support such efforts during a Senate committee hearing in November, saying would need to further examine the issue.

It wasn’t the answer free-speech advocates were hoping for. Members of the coalition said they hope Smith will deliver a stronger rebuke of the proposal on Wednesday.