The obligation arising from a promissory oath ceases: 1/ if it is remitted by the person for whose benefit the oath was made; 2/ if the matter sworn to is substantially changed or if, after the circumstances have changed, it becomes either evil or entirely indif-ferent or, finally, impedes a greater good; 3/ if the purpose or a condition under which the oath may have been taken ceases; 4/ by dispensation or commutation, according to the norm of can. 1203.
Source: Code of Canon Law (Vatican.va)