[EternalVigilance]

When he took the oath of office, he swore to faithfully execute all of the laws passed by the US Congress. To willfully ignore to enforce any law breaks that oath.

True only for laws that are constitutional. If the president believes that some law the Congress has passed is unconstitutional, then, in order to keep his own sacred, binding oath to support the Constitution, he has an obligation to provide the appropriate check and balance on the other branch.

In this case, there is no shadow of any doubt whatsoever that Congress, in Article 1, Section 8, possesses the sole grant of constitutional power to govern immigration and naturalization.

[Synthesist]

That’s true, but at the time a president is sworn into office, most existing law is established. Of course, any new laws that come to him to sign can be vetoed for any reason, including the belief that it is unconstitutional.