A landlord or other person can sue in Landlord and Tenant whenever a person or company is in possession of property but does not have a legal right to be there. Tenants may lose their right to possession by failing to pay rent, violating the lease, violating the housing code, running a "drug-haven," or for certain other reasons recognized by the law. Cases can also be filed to evict trespassers, squatters, and others who do not have a legal right to possess the property.