Universal Studios Sues -- Porn Companies Are Ripping Off '50 Shades of Grey'

You can't just shoot a filthy porno and call it "50 Shades of Grey" -- at least according to Universal Studios, which is now suing several XXX companies for ripping off its "50 Shades" movie rights.

Universal filed the lawsuit against three porn companies, claiming they illegally made an unauthorized film -- called "Fifty Shades of Grey: a XXX Adaptation" -- as well as bootleg "50 Shades"-themed sex toys.

Universal -- along with Fifty Shades Ltd. -- claims the film isn't parody, and therefore isn't protected under the First Amendment.

According to the suit, "The first XXX adaptation ... does not comment on, criticize, or ridicule the originals. It is a rip-off, plain and simple."

The suit continues, "By lifting exact dialogue, characters, events, story, and style from the Fifty Shades trilogy, [producer] Smash Pictures ensured that the first XXX adaptation was, in fact, as close as possible to the original works."

The suit claims two additional XXX films are currently in the works -- and an accompanying sex toy set called "Fifty Shades of Pleasure" has already been released.

Universal wants damages -- plus an injunction blocking any further releases of the film.