Landlord-tenant law governs the rental of commercial and residential property. It is composed primarily of state statutory and common law. A number of states have based their statutory law on either the Uniform Residential Landlord And Tenant Act (URLTA) or the Model Residential Landlord-Tenant Code. Federal statutory law may be a factor in times of national/regional emergencies and in preventing forms of discrimination. 
The basis of the legal relationship between a landlord and tenant is grounded in both contract and property law. The tenant has a property interest in the land (historically a non-freehold estate) for a given period of time. See Real Property. The length of the tenancy may be for a given period of time, for an indefinite period of time, (e.g., renewable/cancelable on a month to month basis), terminable at any time by either party (at will), or at sufferance if the agreement has been terminated and the tenant refuses to leave (holds over). See Restatement of The Law 2d Property: Landlord and Tenant   1.4-1.8. If the tenancy is tenancy for years or periodic the tenant has the right to possess the land, to restrict others (including the landlord) from entering upon it, and to sublease or assign the property. The landlord-tenant agreement may eliminate or limit these rights. The landlord-tenant agreement is normally embodied in a lease. The lease, though not historically or strictly a contract, may be subject to concepts embodied in contract law. See Contracts;  1.103 of the URLTA. 
The landlord-tenant relationship is founded on duties proscribed by either statutory law , the common law, or the individual lease. What provisions may be contained in a lease is normally regulated by statutory law. See  1.403 of the URLTA. Basic to all leases is the implied covenant of quiet enjoyment. This covenant ensure the tenant that his possession will not be disturbed by someone with a superior legal title to the land including the landlord. See Restatement 2d  4.1-4.3. A breach of the covenant of quiet enjoyment may be actual or constructive. A constructive eviction occurs when the landlord causes the premises to become uninhabitable. 
Housing codes were established to ensure that residential rental units were habitable at the time of rental and during the tenancy. Depending on the state, housing code violations may lead to administrative action or to the tenant being allowed to withhold rent. The habitability of a residential rental unit is also ensured by warranties of habitability which are prescribed by common and/or statutory law. See  2.104 of the URLTA. A breach of the warranty of habitability or a covenant within the lease may constitute constructive eviction, allow the tenant to withhold rent, repair the problem and deduct the cost from the rent, or recover damages.
Unless the lease states otherwise there is an assumption that the tenant has a duty to pay rent. State statutes may provide for a reasonable rental value to be paid absent a rental price provision. . In commercial leases rent is commonly calculated in part or whole as a percentage of the tenants sales. Rent acceleration clauses that cause all the rent to become due if the tenant breaches a provision of the lease are common in both residential and commercial leases. Summary eviction statutes commonly allow a landlord to quickly evict a tenant who breaches statutorily specified lease provisions. Self-help as a method of eviction is generally restricted. Some states do not even allow it for tenants who have held over after the end of a lease.. Landlords are also restricted from evicting tenants in retaliation of action the tenant took in regards to enforcing a provision of the lease or applicable law. 

