Many of President Donald Trump's policies have met resistance in federal courts, but anyone challenging the decision to end deportation protections for thousands of immigrants Tuesday will face a difficult legal fight.

Attorney General Jeff Sessions announced Tuesday that the Department of Homeland Security will begin a “wind down” of the Deferred Action for Childhood Arrivals program. Sessions said the administration will end the program “in light of imminent litigation,” a nod to the threat by several Republican state attorneys general to sue if Trump allowed the program to continue past Sept. 5. Now, advocates and state attorneys general are threatening legal action to keep the program in place. Legal experts said such lawsuits could be longshots.

“The reality is that DACA was announced and signed by the secretary of Homeland Security,” said Shoba Sivaprasad Wadhia, a professor at Penn State Law and director of the school's Center for Immigrants' Rights Clinic. “It is a policy document, so it is a tool in administrative law, but it can technically be rescinded, modified, replaced.”