Both liberal and conservative presidents have made choices about whether or not they will enforce particular laws passed by Congress. This is nothing new. It's just getting a lot more media attention than most instances of this have gotten.
(A very common example: many people in the US can walk into a store and buy marijuana without fear of prosecution because the last several presidents -- from both parties -- have chosen not to enforce that particular federal law.)
Certainly the courts can (and sometimes do) get involved, but the only thing that can force the executive branch to act is for the House to impeach the president, and for the Senate to convict. And the House is not going to impeach Trump over this, or pretty much anything.
(A very common example: many people in the US can walk into a store and buy marijuana without fear of prosecution because the last several presidents -- from both parties -- have chosen not to enforce that particular federal law.)
Certainly the courts can (and sometimes do) get involved, but the only thing that can force the executive branch to act is for the House to impeach the president, and for the Senate to convict. And the House is not going to impeach Trump over this, or pretty much anything.