(AP) — More than a dozen University of Kansas students wore empty gun holsters to class to protest the university’s decision to delay implementation of full conceal-and-carry rights on campus.

Kendon Brawner, a student from Lawrence, said the protest Tuesday was intended to spread a message that participants feel gun-free zones aren’t effective in deterring violence by people intent on using firearms illegally.

Under Kansas law, colleges and universities can allow someone with a concealed-gun permit full access to campus buildings, or the schools can request an exemption for up to four years.

The university received an exemption but has to open campus buildings by 2017 to people with conceal-and-carry permits. The university can keep the ban in place if it installs security systems at public building entrances.