Several pro-marijuana activists are seeking an emergency injunction against the University of Colorado’s plans to close its Boulder campus Friday as part of the school’s efforts to stop an annual pot smoke-out and demonstration.

The activists filed suit against the university today in district court in Boulder. They are hoping to get a court hearing by the end of the day, said attorney Rob Corry, who is representing the activists.

The lawsuit seeks to stop CU from closing its campus to non-students without a previously arranged appointment. The closure is designed to prevent people from outside the school from flooding the campus to participate in the annual “4/20” event — at which attendees protest marijuana laws and many light up in unison at 4:20 p.m.

The lawsuit claims the closure stifles the activists’ free speech and is unconstitutionally focused on shutting down a protest based on the protesters’ message.

“CU’s proposed closure of an entire campus to shut down an afternoon protest occurring on a small portion of the campus is without legal support or precedent,” the activists, who are not CU students, contend in their lawsuit.

CU officials have said the closure — and the ending of the 4/20 event, which has attracted upwards of 10,000 people in years past — is needed to protect student safety and prevent disruption to teaching. The school is instead hoping students will attend a free concert by Wyclef Jean at the Coors Events Center. Student leaders and the Boulder City Council have endorsed efforts to stop the demonstration.

Meanwhile, attorney Sean McAllister said CU students who are part of the school’s chapter of Students for Sensible Drug Policy have received permission to hold a protest of the campus closure near Norlin Quad on Friday. The quad is the usual site of the 4/20 gathering, but campus officials plan to close the space Friday to all use and apply a foul-smelling fish-based fertilizer on the grass.

John Ingold: 303-954-1068 or jingold@denverpost.com