Green’s Dictionary of Slang

(US und.) the police.

1970		J. Wambaugh New Centurions 117: ‘La Jura!’ said a voice from the car, apparently seeing the policemen step from the shadows.
1998		Austin American-Statesman (TX) 14 Oct. 9/4: Texas Prison Gangs Slang [...] Jura: Police.
1999		E. Bunker Mr Blue 107: Once I accidentally ran a stop light on Riverside Drive. She said, ‘Trucha . . . la jura!’ It was pure barrio slang for ‘Cool it, the heat.’.