(The WWII-veteran USCGC Cherokee on a 1980s narcotics patrol.)
(A demilitarized WWII-veteran C-46 Commando which crashed while in use as a smuggling plane during the 1980s.)
The US Coast Guard was formed (as the Revenue Cutter Service) on 4 August 1790. The Posse Comitatus law of 1878 restricts use of the American military in law enforcement. However the US Coast Guard is specifically exempted from any restrictions, and in fact law enforcement is one of it’s core missions.
During the Cold War the US Coast Guard’s funding came from the Department Of Transportation, not the Pentagon, and money just to buy fuel was at a premium, let alone new construction. The fleet during President Carter’s term was in a bottleneck; as all Prohibition-era cutters were gone, but new modern hulls were not being launched fast enough to replace them. Some aged WWII ships were pressed into service as cutters.