The outcome in Boise could reverberate in Los Angeles -- where officials are considering resuming enforcement of the city's own anti-camping ordinance, considered among the strictest in the country.
It bans sleeping, sitting or lying on sidewalks and other public property.
In 2006, the 9th U.S. Court of Appeals struck down the ordinance, finding that banning sleeping in public by people who have nowhere else to go violated the 8th Amendment provision barring cruel and unusual punishment.
Two years later, Los Angeles settled a lawsuit by agreeing to suspend enforcement between 9 p.m. and 6 a.m. until additional housing for the homeless could be built.
Earlier this year, officials said they expected to reach the construction milestone the city agreed to as soon as next month. Several officials, including L.A. police Chief Charlie Beck, have said strict enforcement of the anti-camping law could start up again, but the city has issued no formal opinion.
The Justice Department's filing Thursday came in a 2009 lawsuit by seven homeless people convicted of violating a Boise ordinance against sleeping or camping in outdoor public spaces.
The city said the camps were unsafe and unsanitary.
But "if a person literally has nowhere else to go, then enforcement of the anti-camping ordinance against that person criminalizes her for being homeless, " the department said.
"Needlessly pushing homeless individuals into the criminal justice system does nothing to break the cycle of poverty or prevent homelessness in the future," principal Deputy Assistant Atty. Gen. Vanita Gupta said in a statement.
"Instead, it imposes further burdens on scarce judicial and correctional resources, and it can have long-lasting and devastating effects on individuals' lives."
L.A.'s homeless population has grown to 26,000 people as of January -- a 12 % leap in two years. Countywide, the number of people sleeping in outdoor encampments or vehicles jumped 85% in the same period.
More than 70% of homeless people in L.A. County sleep outdoors because of a lack of shelters, a higher rate than in much of the rest of the country, homeless advocates said.
The spread of unsightly encampments has drawn public outcry from businesses and L.A. residents, who say they sow unsanitary conditions and cause petty crime in the communities.
Last month, Los Angeles adopted an ordinance making it easier to dismantle homeless encampments; the city also has stepped up the cleanup of tents and other homeless possessions.
Attorney Carol Sobel, who represented homeless people in the 2006 L.A. case, said the Justice Department filing should be a "strong message they need to go back to drawing board and figure out how to respond to the causes of homelessness and not punish people for their status.
"It's unconscionable to seek to penalize people again for the city's failures," she said.
A spokesman for City Atty.
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