The so-called "Perpetual" Lease of Guantanamo Bay

The 1903 lease documents have no clauses that give a termination date for the lease. The motivation for the lease is the protection of Cuba, and the method is Naval and Coaling Stations. A naval presence allowed the US to remove the US army.
The motivation has been abandoned, and the means are obsolete.

1. No longer necessary as a coaling station
2. No longer necessary as a Naval Station for the mutual defense of the US and Cuba

The lease may be terminated for the reasons that a contract may be terminated, since a lease is a contract.
1. Material breach
Building a prison is a material breach
2. Anticipatory Breach
Kennedy's promise to not invade Cuba is an anticipatory breach of the US's duty to protect Cuban independence.