The Confiscated (1971)

A couple of vice cops, a seasoned vet and a new trainee, travel around San Francisco trying to bust obscenity. The two begin in a Frisco storefront theater scrutinizing the product, then set their sights on a couple rutting lesbians - soon joined by a male companion - on the beach, using a pair of park binoculars to spy on the action. Following the women to their apartment afterward to make a bust, they end up getting seduced by the couple to get off the hook. Besides, the cops have bigger fish to fry, now convinced they've uncovered an underground drug ring and heading to a nearby bar to ferret it out...