U.S. marshals stand at the entrance of Oaksterdam University in Oakland, Calif. on Monday. The federal agents raided the medical marijuana training school at the heart of California’s pot legalization movement.

According to its website, the college offers mostly seminar classes on growing marijuana, but also classes on advocacy, law, economics and agriculture that ties to marijuana.

It claims thousands of students have enrolled at Oaksterdam since it was founded in 2007.