State Assemblyman Rob Bonta (D-Alameda), who authored the bill, said California will prevail because states have the authority to regulate industries within its borders. He pointed to longstanding reports, including by government watchdogs, about substandard conditions, abuses and deaths at privately-run facilities.

“I put my money on California here. We have a constitution on our side,” said Bonta. “States clearly have the ability and the right to stand up for and defend and protect their people and ensure their health, safety and welfare.”

A spokesperson with GEO Group defended the company's operations, saying its facilities "comply with performance-based standards."

“As a service provider to the government, our only mission is to deliver top-rated services to those entrusted to our care as they go through their immigration proceedings," said the GEO Group spokesperson in a statement.

The legal challenge comes just days after U.S. Immigration and Customs Enforcement (ICE) entered into multibillion-dollar contracts with GEO Group and two other private prison companies to keep running detention centers for as long as 15 years, with a combined total of 5,200 beds in the state.

GEO Group currently operates two immigration detention centers in Adelanto (San Bernardino county) and Bakersfield. Under the new agreement with ICE, the company plans to add an additional 2,150 beds by using three other California prisons it owns in the Central Valley town of MacFarland and another in Adelanto, according to a company press release.