Federal law enforcement officers on Monday notified demonstrators camped outside Portland’s Immigration and Customs Enforcement headquarters that they must begin to vacate federal property.

“It is unlawful under federal law to obstruct the entrances, foyers, lobbies, corridors, offices and/or parking lots of federal facilities,” reads the flyer Federal Protective Service agents distributed to protesters, who have blockaded the Southwest Macadam Avenue facility since last week.

Those who obstruct the entrance to the building, according to the flyer, face arrest and prosecution in federal court. However, officials acknowledged they had no authority over adjacent properties owned by other entities.

Activists have waged the round-the-clock occupation in opposition to the Trump administration’s immigration crackdown, including its policy of separating migrant children from their parents at the U.S. border.