He issued that statement while the Republicans controlled both the Senate and House. Under the context of the statement, it sounded more like a challenge to the republican leadership to make sure that such a law never reaches his desk. Whether or not he would have signed it if brought to him by a Democrat controlled congress is debatable. What is not debatable is the fact that any of the current frontrunners most certainly would sign it in a heartbeat, while one Senator from Illinois would probably use the Presidency to push for such a law.