An alienation by a tenant of a part of his lease, reserving to himself a reversion; it differs from an assignment, which is a transfer of all the tenant's interest in the lease. And even a conveyance of the whole estate by the lessee, reserving to himself the rent, with a power of re-entry for non-payment, was held to be, not an assignment, but an underlease.
In leases there is frequently introduced a covenant on the part of the lessee, that he will not underlet the premises, nor assign the lease. This refers to the voluntary act of the tenant, and the covenant is not broken when the lease is transferred without any act on his part; as, if it be sold by the sheriff on execution, or by assignees in bankruptcy, or by an executor. The underlessor has a right to distrain for the rent due to him, which, the assignor of a lease has not. The under-lessee is not liable personally to the original lessor, nor is his property subject to his claim for rent longer than while it is on the leased premises, when it may be distrained upon. The assignee of the lessee stands in a different situation. He is liable to an action by the landlord or his assignee for the rent, upon the ground of privity of estate.