man‧da‧to‧ry / ˈmændət ə ri $ -tɔːri / adjective
if something is mandatory, the law says it must be done SYN compulsory , obligatory → discretionary
mandatory for
Crash helmets are mandatory for motorcyclists.
Murder carries a mandatory life sentence .
The Council has made it mandatory for all nurses to attend a refresher course every three years.