The Supremacy Clause lists the supreme laws in order: constitution, federal statutes, treaties. If there is a conflict among them then it's natural for the cou

The Supremacy Clause lists the supreme laws in order: constitution, federal statutes, treaties. If there is a conflict among them then it's natural for the courts to resolve that conflict by deferring to the more supreme item on that list, thus if a law violates -say- the right to due process as enshrined in the constitution then that law must be invalid and the courts must rule as much. Marbury is an utterly natural consequence of the Supremacy Clause and Article III (and the context of common law).