It doesn't apply to the laws of each of the states (which CC laws are) so much as to court rulings.
***According to the Supreme Court, there is a difference between the credit owed to laws (i.e. legislative measures and common law) as compared to the credit owed to judgments.***
***If the legal pronouncements of one state conflict with the public policy of another state, federal courts in the past have been reluctant to force a state to enforce the pronouncements of another state in contravention of its own public policy***
IOW, if a court decision is based on say, a civil Rights violation, it would apply to citizens in every state....on the other hand, if the decision was based on a state law, it may not apply to citizens of other states.
Edit to remove useless hyperlink