BOULDER, Colo. Stinky fish fertilizer and two dozen law-enforcement officers kept pot smokers away from a grassy quad at the University of Colorado on Friday, but a few hundred protesters defied the crackdown and rallied on another field, where some lit up at 4:20 p.m.

It was a far cry from last years April 20 pot celebration, when more than 10,000 people gathered on the universitys Norlin Quadrangle for the annual ritual of enjoying a smoke and demonstrating for legalizing marijuana.

That made the university the scene of one of the largest campus celebrations of cannabis in the nation a reputation that prompted university administrators to take extraordinary steps to stamp out this years rally.

They banned unauthorized visitors from campus, and spread smelly fertilizer on the Norlin Quad and declared it off-limits. They even booked Haitian-born hip-hop star Wyclef Jean for a free concert timed to coincide with the traditional 4:20 p.m. pot gathering.

Still, they were only partially successful. A few dozen protesters veered off a sidewalk bordering the university on Friday afternoon and marched through campus, holding signs and chanting, Roll it. Smoke it. Legalize it.

Others joined in as the marchers made their way through the campus, and after they halted on a grassy field near a science building, the crowd reached 300, with 400 more watching from the perimeter, campus police estimated.

They counted down the seconds to 4:20 p.m., let out a cheer at zero and then lit up, exhaling a collective cloud of smoke that rose over their heads.

A few police were on hand, some in SWAT gear, but they made no move to interfere. After about 15 minutes the crowd and the smoke dispersed.

Jonathan Grell, a sophomore majoring in international affairs, said he joined the rally because it mocks Americas arcane drug laws.

He said he didnt smoke Friday but has benefited from medical marijuana.

I participated to be counted and to make my voice heard, he said.

James Moore, a graduate student in physics, said he went to the rally to protest the administrations decision to close down part of the campus.

You cant do that, Moore said.

The campus is public property and students pay to attend, he said, and the university has no right to say, No, you cant walk on the grass.