You are correct, it *is* up to congress and the courts to decide on the laws. They have done so, and the executive is not enforcing them.
Santorum is absolutely correct to say that he will enforce the laws congress has passed, unless an until (barring rare times when an executive check would make acting otherwise the right thing to do) the courts rule against them. He should be calling for impeachment for O’s failure to “take Care that the Laws be faithfully executed (USC Art II, section 3), but that won’t happen.
Just curious how this opinion piece got posted as news, let alone posted as breaking news?