Associate professors are non-tenure track employees, and his appointment was probably already up anyway.
You may mean adjunct professors, which are never tenure-track (and loved by administrations because they're cheap and can't complain about administrative bloat). The typical tenure track starts at Assistant Professor with an up or out promotion to Associate Professor (with or without tenure), with a later up or out promotion to Associate Professor with tenure if the first promotion did not permit tenure or to Full Professor if the first promotion included tenure.