Following is/are the requisites for a valid custom

I. Uti Possidetis	1. Principle in customary international law providing that where there has been a fundamental change of circumstances since an agreement was concluded, a party to that agreement may withdraw from or terminate it.
II. Pacta Sunt Servanda	2. Two or more states equally exercise sovereignty with respect to a territory and its inhabitants.
III. Condominium	3. Doctrine that territory remains with the possessor state at the end of war or occupation unless otherwise determined by a treaty or an agreement.
IV. Rebus Sic Stantibus	4. Proposition that treaties are binding upon the parties to them and must be performed in good faith.