His latest setback before the 9th Circuit came on Thursday when a three-judge panel rejected his bid to rescind a program launched by his Democratic predecessor, Barack Obama, that protects from deportation hundreds of thousands of illegal immigrants brought into the country as children.
The decision by the San Francisco-based 9th U.S. Circuit Court of Appeals preserves the Deferred Action for Childhood Arrivals (DACA) programme introduced in 2012 that has shielded from deportation a group of immigrants dubbed "Dreamers" and has given them work permits, though not a path to citizenship.
In Thursday's ruling, 9th Circuit Judge Kim Wardlaw said California and other plaintiffs were likely to succeed with their claim that the decision to end DACA was arbitrary and capricious.
The administration's actions on DACA were prompted by a threat by Texas and other states to sue to end the program.
The court ruled in five lawsuits that were filed by entities including the University of California and the state of California and were handled jointly in Alsup's court.
Trump has taken a stern stance against illegal immigration.
On Monday, the United States Department of Justice and the US solicitor general filed a petition asking the Supreme Court to decide the issue before the ninth circuit court made its decision.
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While the federal government might be able to end DACA for policy reasons under its own discretion, it can't do so based on Sessions' faulty belief that the program exceeds federal authority, the court held.
Last year, the Trump administration announced its plan to phase out the program, but federal courts have ruled that the phase-out could not apply retroactively and that the program should be restarted.
"The reality is (and always has been) that the executive agencies charged with immigration enforcement do not have the resources required to deport every single person present in this country without authorization", she said.
The Justice Department did not immediately respond to a request for comment. It sent a letter to the circuit last month, saying that if the decision was not handed down by October 31, it would ask the Supreme Court to take up the issue.
California, the most populous US state, is a liberal bastion that is unfriendly political territory for Trump. A judge overseeing that lawsuit and four others ruled against the administration and reinstated the programme in January.
The administration then asked the 9th Circuit to throw out Judge Alsup's ruling. Trump administration lawyers have argued that the lawsuit seeks to direct federal environmental and energy policies through the courts instead of through the political process.
UC spokesperson Claire Doan said in a statement the University welcomes the appellate court's decision and is now calling on the Trump administration to stop its efforts to repeal DACA. The high court in February declined to do so.