Answer:
Judiciary
Step-by-step explanation:
The federal government of the United States is made up of 3 branches,
1. Legislative -> Creates laws
2. Judiciary -> Evaluates laws
3. Executive -> Carries out laws
So when a federal court rules on a matter the losing party is always entitled to file an appeal, but just because an appeal is filed does not mean it will be granted, in fact most appeals don't even make it to appeals. I'm not going to detail every possible outcome because the court system is very complex and my knowledge of it only goes so far. Ultimately the highest court in the U.S is the supreme court, which is the head of the Judicial branch.