What is the relationship between the states concerning their laws in the Constitution?

Answer 1

There are several provisions of the Constitution that impact on the relationship between the states.

First, Article I, Section 10 lists several types of laws that a state may not pass without the consent of Congress. The most crucial of these is that the consent of Congress is required for any compact between states.

Second, the Commerce Clause, Article I, Section 8, clause 3 (giving Congress the authority to regulate interstate commerce) has been interpreted as implicitly banning any state law that creates a competitive advantage for goods produced in-state when compared to goods produced in other states.

Third, the privileges and immunities clause, Article IV, Section 2, clause I, prohibits a state from certain types of discrimination against non-residents.

Fourth, the Full Faith and Credit Clause, Article IV, Section 1, requires states to give full faith and credit to the laws, public records, and judicial judgments of other states.

Answer 2

Not exactly sure what you are asking, but the States are required to follow all laws in the Constitution.

A state may make no laws that infringe on the Constitution.