Answer:
principle of supremacy
Step-by-step explanation:
The principle of supremacy is a European Union law according to which whenever there is a dispute between a European Union law and a law of another member state, the law of European Union will be applicable and it will prevail. The national law is to be set aside in such a condition.
Hence, if Texas and Mexico sign a trade agreement, the U.S Constitution has the power to object is based on the principle of supremacy.