A Boulder district judge denied an emergency request to block the University of Colorado from closing the Boulder campus to visitors in its effort to end the annual 4/20 smokeout.

Judge Andrew Macdonald made the ruling after a nearly four-hour hearing Thursday, the eve of the unsanctioned pro-marijuana holiday.

The lawsuit seeking the injunction was filed Thursday morning by six plaintiffs -- Rob Smoke, Timothy Tipton, Jack Branson, Katherine Cummins, Evan Ravitz and Tom Cummins -- all of whom are not CU students and wanted to participate in the event.

Their attorney Robert Corry, who has been a prominent voice for marijuana legalization and the rights of medical marijuana patients, argued that CU had no grounds to close the campus to non-students.

But the judge said CU is well within its rights to regulate the campus.

The university announced April 13 that the campus will be closed to the public Friday, and students and faculty members will be required to show a BuffOne card to access the campus. The Norlin Quad -- where the pot smokeout typically takes place -- also will be closed to everyone including students, and fish-based fertilizer will cover the lawn.

Macdonald said he did not think the measures are unreasonable because the closures will be only for one day, and the university did put in place a process by which people could apply for permits to be on the campus during 4/20.

Two student groups -- a student chapter of the American Civil Liberties Union and Students for Sensible Drug Policy -- applied for permits and will hold events at the Dalton Trumbo fountain near the University Memorial Center.

None of the six plaintiffs applied for a permit.

"We're not looking at an application that was denied," the judge said. "The university has the right to impose these regulations on campus."

Corry said no public university has ever closed its campus to the public, and he likened the measures to "killing a fly with a sledgehammer."

"In this case, the University of Colorado has taken a step no public university in the history of the United States has taken," he said. "If we can't have a free marketplace of ideas on a public university campus, then where can it occur in the U.S.?"

CU acknowledged the closure was unprecedented but said the annual 4/20 gathering is an "unusual" event.