PHOENIX -- Twice defeated in her attempts to limit the voter-approved medical marijuana law, Gov. Jan Brewer on Tuesday set the stage for a third court battle.

The governor signed legislation to make college and university campuses off-limits to those who are legally allowed to possess and use the drug everywhere else. Brewer press aide Matthew Benson said his boss believes marijuana does not belong there.

But a spokesman for a group involved in convincing voters to adopt the law two years ago already has predicted the new law will be challenged. Joe Yuhas said lawmakers and Brewer are constitutionally precluded from imposing the restriction, no matter how much support it has at the Capitol.

The 2010 initiative allows those with a doctor's recommendation for certain specified medical conditions to get a state-issued card allowing them to obtain up to 2 1/2 ounces of marijuana every two weeks for personal use.

There are limits, including possessing marijuana on the grounds of any primary or secondary school, and smoking marijuana on public buses or in any public place.

This new law, set to take effect this summer, says no one -- including those with medical marijuana cards -- can possess or use marijuana on the campus of any public university, college, community college or post secondary institution.

Rep. Amanda Reeve, R-Phoenix, said the legislation was requested by college officials.

They said campuses are required to have policies that make their campuses free of illegal drugs. And while the initiative made marijuana legal by some under state law, its possession remains a felony under federal statutes.

Reeve said allowing medical marijuana onto campuses could endanger federal grants to the schools and federal aid to students.