Selena Gomez Subpoenaed For Justin Bieber's Bedroom Secrets

Selena Gomez is being dragged into Justin Bieber's legal messes -- she was just subpoenaed to testify in one of Bieber's photog-beating lawsuits ... but the upside, Selena's legs LOOKED FANTASTIC.

Sources connected to the case tell TMZ ... the summons is for a deposition in a lawsuit filed by an L.A. pap who claims Bieber karate kicked him in the stomach back in 2012.

The pap says Selena was right there, so they want her under oath, giving a blow-by-blow. But we're told even more important is her pillow talk with Justin -- revealing his bitter feelings and short trigger when it comes to paparazzi.

Selena is becoming a popular witnesses. The photog in the Miami beating case also wants to question her under oath. She wasn't there for the alleged attack, so it's all about pillow talk.

But again ... what it really comes down to is ... she has great legs.