The National Park Service said Friday that it will begin enforcing its long-standing regulation prohibiting camping on federal parkland at the Occupy sites at McPherson Square and Freedom Plaza at noon Monday.

To be compliant with the no-camping rules, protesters must remove all evidence of camping from the park, including bedding, storage containers and anything used to make a fire, the Park Service said.

McPherson Square protester Sam Jewler said that some of the occupiers would be willing to risk arrest Monday.

“Many of us will be likely to defend the park with the passion anyone would show defending their home,” Jewler said. “We are fighting for the betterment of D.C., America and the world, and we intend to continue using our First Amendment rights to do so.”

The Park Service distributed fliers at both sites Friday that detailed the no-camping regulations and noted that they had “repeatedly advised participants” of the rules and had sought “voluntarily compliance.” NPS has said that U.S. Park Police will encourage protesters to sleep elsewhere, and if they refuse to leave Monday, they could risk citation or arrest.

Three protesters were arrested at the park early Friday, but Carol Johnson, the spokeswoman for the National Mall and Memorial Parks, said that they were not charged with camping. Rather, two of the protesters were charged with disorderly conduct and one with an outstanding warrant for another offense.

Sara Shaw, a protester from McPherson Square, had tweeted throughout the morning hours that police officers were checking tents.

The Park Service has long supported protesters’ right to conduct a “24-hour vigil” in the camps at McPherson Square and Freedom Plaza, where protesters have been living in solidarity with the Occupy Wall Street movement since October, installing portable toilets — and in the case of Freedom Plaza, a full-service kitchen. The camps have come under fire recently because of health and safety concerns.

The Park Service on Friday noted that examples of ongoing “compliant” 24-hour vigils have gone on at Lafayette Square and the Vietnam Veterans Memorial for years. But they say overnight camping is a no-no.

“The National Park Service takes very seriously its tradition of providing opportunities for First Amendment activities,” Bob Vogel, superintendent of the National Mall and Memorial Parks, said in a statement. “We have a long history spanning several decades of 24-hour First Amendment vigils.”

National Park Service Director Jonathan B. Jarvis had said at a congressional subcommittee hearing looking into the Occupy situation at McPherson Square on Tuesday that the U.S. Park Police would soon begin enforcement of their own no-camping regulations.