Asking for advice on father not respecting my sister's boundaries

So me, my sister, and my mom live in our house together, and my mom is letting her ex(my dad) live here for a bit, but he hasn't respected my sister's boundaries AT ALL. Me and my sister are both teens, which makes this piss us off even more. He's constantly hugged her and headlocked her without permission when she has clearly stated she does not want to be touched, and he doesn't stop. He also barges into her room, scolds her sometimes, and rips her blanket off when she's trying to sleep. Our mom won't kick him out, and doesn't care.

Any advice?