"At one's discretion" is a term that suggests a decision has been left entirely up to an individual. Antonyms for this expression include inflexibility, lack of choice, and restriction. When something is not at one's discretion, it could be mandatory, compulsory, or mandated. This implies there is little scope for an individual to deviate or make choices on their own. In contrast, terms like obligation, duty, and requirement emphasize the absence of choice, indicating that an individual is limited in their decision-making abilities. Overall, the antonyms for "at one's discretion" suggest a lack of autonomy and emphasize the importance of external factors in determining the outcome of a situation.