For once, I don't think those contractors will go straight to war crimes. In Iraq and Afghanistan their main orders were to provide security. Unfortunately that meant that they couldn't scratch their itchy trigger fingers. This time around, thanks to Russia flooding the lines with meat, they'll have a target rich environment in which to play with their toys. They'll be too busy playing John Wick against poorly trained ex-cons and conscripts to accidentally kill any women and children.
At the risk of being too credible, I should point out that contractors don't necessarily mean PMC and most of the time they're just maintenance/support types.