I am unaware of it being repealed. As I mentioned, diplomatic credentials were handed out by states in the 80s until the Office of Foreign Missions was established. AFAIK, that didn't necessarily mean the states couldn't do it anymore just that the OFM started doing it so they didn't have to.
Consider the significance that all U.S.A. Secretaries of State issue Apostilles rather than one. Apostilles are diplomatic in nature.