The president's new policy relies on prosecutorial discretion, a nice term for using the government's resources to deport the bad guys criminals, people who repeatedly cross the border illegally, risks to national security and letting the small fish go. Prosecutors make those kinds of practical decisions every day. They have to. There's only so much manpower and money to go around. That's why it's good to set priorities.
What the president is saying in this case is that we, as a nation, don't see that much is to be gained by deporting young people who are willing to finish high school and go on to college, or serve honorably in the military and gain an honorable discharge. These are the young people they have to be 30 years old or younger who are going to contribute to society, to launch careers and start businesses. It's a waste to spend time and money kicking them out of the country.
Any reprieve granted to such a young alien will be temporary. It will last for two years, but will be renewable. In the meantime, the person can apply for permission to work.
The president's political opponents are outraged. They argue that the president is essentially imposing the Dream Act by executive fiat. The Dream Act is a bill that would provide undocumented aliens who were brought to this country as children a path to legal status. Congress has never passed the Dream Act, and Republicans are screaming that the president's action is an unconstitutional end run.
As a political maneuver, the president's move is an end run around a Congress that is incapable of immigration reform. He's trying to woo Hispanic voters who are not happy with his vigorous border enforcement.
But the cry of "unconstitutional" is overwrought. The president isn't changing immigration law, he's changing priorities in the way it's enforced. That's a subtle but important distinction. And it's the right thing to do.