take a firm line (on or against something)

To publicly assert one's opinion or defense of or opposition to something without relenting. I know voicing my opinion on this legislation may put my job in jeopardy, but it's time to take a firm line against these discriminatory hiring practices. Though an unpopular opinion, the principal took a firm line on keeping classes separated by gender.

take a firm ˈline/ˈstand (on/against something)

make your beliefs known and try to make others follow them: We need to take a firm line on tobacco advertising. ♢ They took a firm stand against drugs in the school.