Actually it should have already been in the lease. However if the lease runs out, the tenant and the land lord must follow the previous lease. Anyting including the amount of rent that changes, should have a new lease.
If there is no lease, sorry, the landlord can do whatever he wants.
Also note, landlords are required by law to return your security deposit, less luniveable damages, i.e. large holes in the walls. If the land lord made you pay for rent on your pets, pet stains on the carpet come within the pets terms of "living" however scratched woodwork does not. Go figure.