The Justice Department argued last week in an obscure legal case in Boise, Idaho, that the city's laws banning people from sleeping or camping in public places are unconstitutional. The DOJ's statement of interest, first reported on by The Washington Post, could have implications for cities across the country with similar laws on the books that criminalize people, usually homeless, who sleep outside.

Per the DOJ's filing: "When adequate shelter space exists, individuals have a choice about whether or not to sleep in public. However, when adequate shelter space does not exist, there is no meaningful distinction between the status of being homeless and the conduct of sleeping in public. Sleeping is a life-sustaining activity - i.e., it must occur at some time in some place. If a person literally has nowhere else to go, then enforcement of the anti-camping ordinance against that person criminalizes her for being homeless."

That being the case, the DOJ argues that prosecuting people for sleeping in public constitutes a "cruel and unusual punishment" and is an unconstitutional violation of the Eighth Amendment.

The issue marks the first time that the DOJ has weighed in on this still unsettled area of the law, and it carries huge implications.

A report last year from the National Law Center on Homelessness & Poverty found that out of 187 cities surveyed, 34 percent had citywide ordinances banning camping in public. An additional 43 percent banned sleeping in vehicles and 53 percent prohibited sitting or lying down in public places. On an average night, there are about 150,000 unsheltered homeless people in the U.S.

"All of these laws criminalize the kind of activities - sitting, resting, sleeping - that are arguably fundamental to human existence," the Post's Emily Badger wrote. "And they've criminalized that behavior in an environment where most cities have far more homeless than shelter beds."

The DOJ is basing its argument on a previous Ninth Circuit court decision that struck down an anti-vagrancy law in Los Angeles.

"That logic specifically says it's unconstitutional to punish people for sleeping outside if there aren't enough beds for them to sleep indoors," Badger wrote. "If there are, the constitutional question would be different, although the moral and policy implications may remain the same."