act within (one's) rights

To take a certain action that is permitted or justified by the law. You may find his lawn signs offensive, but they're on his property—he's acting well within his rights to put them there. They were acting within their rights when they denied entry to the man, who tried to get on the plane in an intoxicated and unruly state. If she thinks she was wrongly terminated, then she's acting within her rights to file a lawsuit against the company.