The phrase "declaring null and void" refers to cancelling something entirely, but what are the opposite words that can be used? In such instances, one might want to consider terms that imply validation, acceptance, or retention. Therefore, some options for antonyms for declaring null and void include words such as approve, validate, authorize, affirm, certify, endorse, recognize, confirm, ratify, and sanction. These expressions denote that something is legitimate, effective, and not subject to revocation or annulment. When it comes to the opposite of cancelling or revoking, these phrases can portray the idea of affirming or acknowledging with some degree of permanence.