Kim, Khloe, Kourtney Block Blac Chyna's Kardashian Trademark

Just because Blac Chyna's marrying a Kardashian doesn't mean she can get in the club -- the Kardashian sisters are going to war to block her from cashing in on the family name.

According to docs obtained by TMZ ... Kim, Khloe, and Kourtney's companies are opposing Chyna's request to trademark "Angela Renee Kardashian" -- which she was trying to lock down for use while working in entertainment, and also on social media.

The mean girls sisters throw down the gauntlet in docs, saying if Chyna gets the trademark they'll "suffer damage including irreparable injury to their reputation and goodwill."

Translation: stay in your ex-stripper lane ... you're not one of us.

Make no mistake ... this is nasty. In the docs, they say Chyna is "deliberately seeking to profit from the goodwill and popularity" of the Kardashian name.