Hundreds of protesters gathered outside the Supreme Court Tuesday as justices heard arguments on the Delayed Action for Childhood Arrivals (DACA) program.
DACA has allowed hundreds of thousands of so-called "Dreamers" brought to the United States illegally as children to avoid deportation.
The Trump administration says DACA is unconstitutional and argued President Trump had no choice but to end the program, which President Obama created by executive memorandum in 2012.
Prior to the hearing, President Trump tweeted that many DACA recipients are "far from angels," calling them "very tough, hardened criminals." However, people convicted of serious crimes are not eligible for the program.
Court watchers say, based on their questions during the 80-minute session, it appears the court's conservative majority seems likely to side with the Trump administration.
It's unclear what would happen to DACA recipients if the court rules against them.
In June, the House passed a bill which would make DACA the law of the land but the Senate has not acted on it.