Crowds of thousands of pot-smokers have clashed with police in the past on Farrand Field on April 20. Last year, 2,500 people converged on the field, where police took their pictures and later ticketed dozens of them.

Farrand Field is closed forrenovations this year, and students say the smoking festivities will likely take place on the nearby Norlin Quad. The unofficial gathering is said to have grown from a northern California tradition of lighting up at 4:20 p.m.

But officials from two pro-legalization groups say they're going to be giving "smoke-free" speeches and concerts and handing out promotional materials to support their cause outside the University Memorial Center.

They say they'll have more credibility if they're talking about how the law should be changed rather than publicly breaking it.

"I don't know that public marijuana use is the best way to try and change the marijuana laws, but it certainly just goes to show that these laws aren't working and people aren't following them," said Mason Tvert, head of the pro-pot group Safer Alternative For Enjoyable Recreation. "We're trying to make 4/20 an event about marijuana reform
rather than just marijuana use."

CU student Summer Weirich echoed that sentiment.

"We're trying to put the emphasis on the activism side of things," said Weirich, who last month created a campus chapter of the National Organization for the Reform of Marijuana Laws. "The thing is, we are not sanctioning that event on the field. We're not saying, 'Go out and smoke on the Norlin Quad.'"

Weirich said she'll probably go out to the field but that she won't be smoking pot: "I don't want to get arrested," she said.

It's not clear how many would-be 4/20 participants share that view. A group on the social networking site Facebook.com called "Come 4/20,

Farrand Field Will Have Grass On It Whether Its Finished Or Not!" boasts 336 members, although the student who created the group said he did it as a joke.

Police aren't counting on a smoke-free day.

"People's right to free speech is absolute, until they cross a line," CU Police Cmdr. Brad Wiesley said. "If people want to stand up and say marijuana should be legalized, that's great. You can protest and make a point without breaking the law to do that."

Wiesley declined to discuss exactly how police will respond to groups of pot-smokers who may emerge on Friday. In the past, police have tried to deter smokers by turning on sprinklers and barricading Farrand Field.

"We're certainly not giving out our entire operational plan. We're not giving out our playbook to the other team," Wiesley said. "We will have a presence. We will be there."