Ignoring constitutional court rulings violates the constitution.
Ignoring court rulings requiring him to violate the constitution, is something he's required to do, under his oath which constrains his authority to a narrowly defined scope.
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people
POTUS has no power to execute an unconstitutional law
Ignoring court rulings requiring him to violate the constitution, is something he's required to do, under his oath which constrains his authority to a narrowly defined scope.