Two points. First, all enforcement action is discretionary. There are all sorts of games played by prosecutors and charging officials during the general run of the mill enforcement activity. Second, all enforcement is initiated by the executive branch of government.
So, when a government charging official fails to act according to the law, the only remedy is removal from office. The executive isn't going to charge himself; and if Obama has ordered the bureaucrats to break the law, they will also enjoy immunity from prosecution because Obama will also order his attorneys general to ignore dereliction of enforcement of immigration law.
I think a more general proposition is that enforcers are NOT breaking the law when they fail to enforce. The "illegal" EO is just a policy implementation respecting enforcement of immigration law. If the people don't like the fact that the executive is not enforcing the law, the people have the tool of replacement, and in extreme circumstances, impeachment.
And remember that the amnesty action may not be breaking the law. Impeachment/conviction doesn’t need to be for law breaking. McCarthy explains this. It’s a political move, not necessarily legal.