It is legally possible to evict a tenant who doesn't have a lease, according to Pine Tree Legal Assistance. Landlords don't need a valid reason for evicting at-will tenants, but they do have to give the tenant anywhere from seven to 30 days of notice in writing.
If a landlord evicts a tenant who doesn't have a lease without warning, they have to inform the tenant of their right to go before a court and contest the eviction, which is known as a "Notice to Quit," states Pine Tree Legal Assistance.
With a seven-day eviction notice, the tenant has to have done substantial and unrepaired damage to the unit, acted as a disturbance to the other tenants, made the unit inhospitable, changed the locks without giving the landlord a copy of the key or is seven days or more behind on paying their rent. Either the landlord or one of their agents is legally required to deliver the Notice to Quit in person. According to Pine Street Legal Assistance, if the landlord has made three efforts to deliver the notice in good faith, then they are allowed to either mail the notice or drop a copy off at the tenant's home.