My father rented a roon to a tenant who became abusive to him he gave her 30day eviction and on the day after he took keys back then the next day she came with the police who made my dad give back keys and said she had theright to be there how can that be true if her eviction date has already passed.

ANY question on law needs to include your general locale as laws vary by area. Did she voluntarily hand over the keys or did he take them.

Only a court can issue an eviction order. That is probably why the police allowed her back.

He gave a 30 day eviction notice, if they don't leave, then he files for eviction in court, only the court actually evicts.

He can not just take the key back if she will not give it, until the court rules