The 2-1 decision from the U.S. Court of Appeals for the 9th Circuit said California's law doesn't circumvent federal authority when it comes to immigration issues.
In dropping the Obama-era order to phase out private prisons, Sessions writes that a return to earlier methods allows the flexibility "to meet the future needs of the federal correctional system."
A promised crackdown on people living in this country illegally could mean a boon for private prison companies that contract with the government to hold detainees.
A court ordered the release of women and children held in immigrant detention centers in favor of electronic monitoring. The GEO Group operates both. Advocates say that's a conflict of interest.
A riot at a private immigration prison in Willacy County, Texas, forced officials to close the facility and relocate 2,800 inmates. But it also left the county with a $2.3 million budget shortfall.