The phrase "declares invalid" is often used in legal contexts to mean that something has been deemed legally invalid or without effect. Antonyms for this phrase might include "validates," "affirms," or "upholds." For example, if a court "validates" a contract, it means that the contract is legally binding and enforceable. Similarly, if a judge "affirms" a decision, it means that the decision has been upheld and is still valid. Other antonyms for "declares invalid" could include terms like "approves," "certifies," or "confirms," which all suggest a positive or affirmative action rather than a negative one.