The phrase "according to regulation" is commonly used to indicate that something is being done in compliance with a specific set of rules or guidelines. In order to convey this meaning, there are a number of synonyms that can be used, such as "in accordance with regulations," "following regulatory protocol," "in compliance with rules," and "in adherence to guidelines." These phrases all indicate the same idea and can be used interchangeably. In professional and legal contexts, it's important to be precise with language, so using these synonyms can help ensure that your meaning is clear and unambiguous.