When Sonny confronts the FBI agent during the wedding reception, the agent does not display his badge.
I also question the agents recording license plates numbers since they appear to be trespassing. The cars were parked on the compound; that area does not appear to be right of way or property accessible by the public unless invited.
oli, I think you're forgetting that this was 1945 and not today. This was not a time when Tom Hagen would have made a legal argument about the FBI overstepping their legal limits.
