As per Lawkidunya, Illegal Possession of Immovable Property, if a person, who is not the legal owner of a property, occupies it without the owner’s consent, it would amount to illegal possession of the property. As long as the occupant has the owner’s permission to use the premises, the arrangement would have a legal validity.

Punishment of Illegal Possession of Land in Pakistan
As per Lawkidunya, Whoever as a property grabber is involved in an illegal possession or illegal dispossession is punishable with imprisonment and fine.