It’s unconstitutional to ban the homeless from sleeping outside, the federal government says

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. - DOJ

More at http://www.washingtonpost.com/news/wonkblog/wp/2015/08/13/its-unconstitutional-to-ban-the-homeless-from-sleeping-outside-the-federal-government-says/

Or the statement of interest itself: http://www.justice.gov/opa/file/643766/download