Joan Rivers HANDCUFFS Herself to Shopping Cart in Anti-Costco Protest

Cops were called to an L.A. Costco yesterday -- after comedian Joan Rivers HANDCUFFED herself to a shopping cart during a one-woman protest against the wholesale store ... comparing the place to "Nazi Germany" ... and we got video of the entire debacle.

TMZ broke the story ... Joan claims Costco banned her new book "I Hate Everything ... Starting with Me" because of several racy jokes on the back cover -- so yesterday, she staged a protest in Burbank against what she called unjust censorship.

Joan yelled into a bullhorn, "Costco should not be like Nazi Germany. Next thing they'll be burning the bible."

Joan then walked into the store and handcuffed herself to a random woman's shopping cart, where she continued to scream. Costco management called the cops, who then asked Joan to leave -- which she did. And that was that.