The United States Post Office, the FBI and the FCC all investigated the song for obscenity. The FCC’s report declared Jack Ely’s singing “unintelligble at any speed we play it.” You can read the FBI’s case file here, but don’t expect to read Jack Ely’s testimony; by then he had left the band and the feds, seemingly unknowingly, interviewed his replacement.
ps — how long before the Post Office that once investigated it puts the song on a stamp? Although the campaign to have “Louie Louie” declared the state song failed, the Washington State Senate declared April 14. 1985 “Louie Louie Day.”