The decision established that treaties, which are described in the Supremacy Clause of the US Constitution as "the supreme law of the land" equal to any domestic federal law, do not hold a privileged position above other acts of Congress. So, other laws affecting the "enforcement, modification, or repeal" of treaties are legitimate.
The decision clarified that treaties, which in the Supremacy Clause of the US Constitution are described as "the supreme law of the land" equal to any domestic federal law, do not have a unique position above other acts of Congress. Consequently, laws affecting the "enforcement, modification, or repeal" of treaties are legitimate.