Continue that hypothetical further: the case makes its way to the Supreme Court, who agrees with the federal judge. The executive branch continues to ignore the order. The Attorney General is held in contempt of court and fined a large amount of money. Who's going to collect it? Any executive branch employee trying to carry out that fine would be violating this executive order, and be dismissed. So the fine would never happen.
Considering the president and vice president's recent disdain for judicial rulings against them, this may happen.