Casey Anthony 911 Call After Bar Fight With Archenemies

Casey Anthony knows a thing or 2 about the law, because she's conversant with the meaning of a police incident report ... something she requested from the 911 operator after a woman allegedly threw a drink on her ... a woman who dated the same man as Anthony.

TMZ has obtained the 911 audio of a call Casey made last week in West Palm Beach, claiming the other woman has been harassing her over an ex they'd both dated. She claimed to have been the recipient of a free drink ... which she says the other lady hurled at her.

Casey is clearly agitated but hellbent on getting the alleged incident documented so she could file for a restraining order. Casey claimed she had been repeatedly harassed by the woman.

Here's what's strange ... as eager as Casey seemed to go down the path of getting a restraining order, when push came to shove she backed off when cops arrived and spoke with her. The other woman had already left the bar.