One of the reasons the Articles of Confederation failed was that states did not have to recognize the laws of other states.

The Full Faith and Credit clause in the Constitution was tested multiple times, most famously with the Dred Scott case, where it was ruled a free state had to give full faith and credit to the laws of a slave state. And that was a good thing.

Gay marriage and adoption, legalized marijuana- states still want to ignore the laws of other states. But we have Full Faith and Credit. Its time state governments were reminded of that.