Scott Weiland's ex-wife needed cops to keep the peace after going nuclear when she was barred from taking some of his instruments.
Law enforcement sources tell TMZ ... officers were called to a recording studio in Burbank, CA last week -- where Scott's ex, Mary Forsberg, was causing a scene while trying to make off with a keepsake.
Mary showed up with her and Scott's teenage son -- we're told he wanted one of his dad's guitars -- but an employee of the recording studio refused to give them access.
An argument ensued ... and cops were called to calm everyone down.
Mary was told it was a civil issue ... and would need her lawyer to work out any division of property.
The tension's been building -- as we first reported, Mary filed docs stating Scott wanted her, not widow, Jamie Weiland, to be executor of his will.
Start the countdown to a lawsuit.