In a rare re-entry onto the political stage, Obama used a Facebook post to slam Trump's decision and call on Congress to step in.
"To target these young people is wrong -- because they have done nothing wrong. It is self-defeating -- because they want to start new businesses, staff our labs, serve in our military, and otherwise contribute to the country we love. And it is cruel," he wrote.
US Attorney General Jeff Sessions, defending the move, said there needs to be a lawful system of immigration that serves national interest and not everyone can be admitted into the country.