The Situation -- BANNED from Showing Abs in Rehab

The Situation must be going through an identity crisis in rehab -- because TMZ has learned, the treatment facility BANS excess skin exposure ... including abs ... as well as douchebag clothing.

TMZ obtained a copy of the "wardrobe guidelines" from Cirque Lodge in Utah -- where Sitch is currently undergoing treatment for substance abuse -- and according to the doc, Cirque bans muscle shirts, sleeveless tops, ripped jeans, hats, sunglasses, and all clothing with obscene language.

In other words -- 99.999% of Situation's clothing collection.

The guidelines also specify "no abdominal exposure" -- a rule intended for the female population -- but given the guy's claim to fame ... it clearly also applies to Mr. Sitch.