Breitbart Big Government reports Rep. Steve King (R-IA) believes the House will immediately begin impeachment activities against President Obama if he tries to give legal status to millions of illegal aliens. Meanwhile, the Prez appears to think maybe being impeached by the House would be a good thing, since there's no way he'd lose a trial in the Senate.
Things could get very weird in the next couple or three months. Obama might try to push Republicans "over the edge" to impeachment prior to the November election, as a way to motivate "his" voters to come out for an otherwise boring-to-them midterm election.
We really have no good model of how to bring to heel a U.S. President who is a scofflaw, all the usual enforcers work for him. I can imagine the Supremes finding he has acted in violation of the law, but I have no idea who'd carry out their decision - for sure Atty. Gen. Holder won't. Harry Reid's Senate Democrats won't.
The closest analog to what might happen here was the situation some years back in Honduras where elected President Manuel Zelaya started doing unlawful things to run for another term when that option was blocked by Honduran constitutional term limits. After their Supreme Court ruled him out of order, their legislative body had him arrested and sent packing into exile. He has since returned to Honduras, not as President.