The most pressing problem with Obama's action is that it's entirely at odds with our U.S. Constitution that only allows laws to presented by the House of Representatives, accepted by the Senate and presented to the President for signature or veto.
The wording is very specific, but Obama feels he can (and has in the recent past) modify, ignoere or, as in this case, formulate a law entirely devoid of any input by both houses of Congress.
His purpose in doing so is entirely and brazenly political. In our mid-term elections held in early November, his Democratic Party took an unprecedented drubbing, losing control of the Senate and losing even more seats in the already Republican dominated House of Representatives. The American people are truly fed up with his arrogance and outright incompetence. He does, however have a core base of supporters... persons of 'color' at the center. His hope is that imposing a restriction on deporting illegals is that, now, they will be added to his 'base' and then help in the Presidential election coming in 2016...
Unfortunately, those newly elected in November won't take office until January so he's still supported by a Senate full of crap Democrats bent on destroying the country as we know it...