WASHINGTON (Reuters) - The U.S. Supreme Court on Monday required Arizona to continue to issue driver’s licenses to the young adult immigrants known as Dreamers, refusing to hear the state’s challenge to an Obama-era program that protects hundreds of thousands of people brought into the country illegally as children.

The case centred on the Deferred Action for Childhood Arrivals (DACA) program created in 2012 under Democratic former President Barack Obama that Republican President Donald Trump already has sought to rescind. Those who signed up for DACA are shielded from deportation and given work permits.

The high court refused to hear Republican-governed Arizona’s appeal of a lower court ruling that barred the state from denying driver’s licenses to people protected under DACA.

Mark Brnovich, Arizona’s Republican attorney general, expressed disappointment that the justices sidestepped the issue of whether Obama had the authority to create DACA.

“Our case has always been about more than just driver’s licenses,” Brnovich said in a statement. “It’s about the separation of powers and whether the president, any president, can unilaterally act and bypass Congress to create new laws.”

The American Civil Liberties Union sued Arizona on behalf of a group of DACA recipients who were denied driver’s licenses, saying the state had infringed on federal powers to make immigration policy. Arizona was the only state to deny licenses to DACA recipients, according to court papers.

“Arizona’s inexplicable attempt to deny driver’s licenses to Dreamers, pursued by two governors for years, has now failed at every level of the federal judiciary,” ACLU attorney Jennifer Chang Newell said.

The justices on Feb. 26 required the Trump administration to keep DACA in place at least for now, turning away its appeal of a judge’s nationwide injunction that halted the president’s September order to begin winding down the program in March.

The Trump administration had urged the justices not to hear Arizona’s appeal, saying the president’s move to rescind the policy means the state’s concerns have already been addressed.

A second federal judge has issued a similar injunction keeping DACA in place.

After DACA was implemented under Obama, Arizona’s governor at the time, Republican Jan Brewer, directed state officials to prevent the program’s recipients from obtaining a driver’s license in the state.

Non-citizens must prove they are authorized to be in the United States to obtain an Arizona driver’s license, such as with a valid federal work permit. The state decided not to accept permits obtained by DACA recipients.

DACA recipients are called Dreamers in reference to legislation that has failed to pass in the U.S. Congress called the DREAM Act, short for Development, Relief and Education for Alien Minors Act.

The San Francisco-based 9th U.S. Circuit Court of Appeals last year struck down the Arizona policy, ruling that the state cannot develop its own definition of immigrants who are authorized to be in the United States and that only the federal government had that power.

Arizona appealed to the Supreme Court, saying the 9th Circuit’s decision ran roughshod over state sovereignty. Arizona said DACA was enacted through a Department of Homeland Security memo, not legislation in the U.S. Congress or a formal agency rule-making process, and could not supersede state law regulating driver’s licenses.