As the government “shutdown” drags on, Washington’s National Mall remains closed to the general public. Not everyone, however, is forbidden to set foot on the mall. The National Park Service (NPS) has posted signs indicating that certain portions of the mall are closed “except for 1st Amendment activities.”

A planned immigration rally also took place on the mall on Tuesday with NPS approval. Susana Flores, a spokesperson for Camino Americano, a group that organized the rally, told the Washington Examiner that the NPS allowed the event to take place under the group’s rights granted by the First Amendment.

Ironically, in posting these signs, NPS has violated the Constitution. Americans may not be forced to guess at what they can do on government property—on pain of fines and jail time if they guess wrong.

Restrictions on speech on public property have inspired a highly complex body of case law. The National Mall is a “traditional public forum.” To borrow from Perry Educational Association v. Perry Local Educators’ Association (1983), the mall “by long tradition or by government fiat has been devoted to assembly and debate.”

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