The phrase "be at liberty to do something" means to have the freedom or permission to do something without any restrictions or obligations. There are several synonyms for this phrase, including "have the right to," "have the privilege of," "have the authority to," "be empowered to," and "be entitled to." These synonyms all convey a sense of freedom and independence when it comes to making choices and taking actions. They suggest that a person has the power and ability to act on their own terms, without being constrained by external forces or obligations. Overall, the phrase "be at liberty to do something" and its synonyms emphasize the importance of personal agency and autonomy.