On Friday, the University of Colorado Boulder announced that on April 20 it will close the entire campus to all visitors as part of a continuing effort to stop the popular 4/20 marijuana smoke out in Norlin Quad, in what is the most aggressive move to date by campus officials to end the gathering.

CU-Boulder Chancellor Philip P. DiStefano made this statement about the reasons for employing such extreme measures to end the gathering via the school's website:

The gathering disrupts teaching and research right in the heart of the campus. The size of the crowd has become unmanageable, and limits our faculty, staff and students from getting to class, entering buildings and doing their basic work. It needs to end.

However, classes will continue as scheduled on April 20 and the campus will remain open to all CU-Boulder students, faculty and staff, but they will need their BuffOne ID cards to get on, and around, the campus, a press release from CU-Boulder states.

Police will be dispersed around campus and will have checkpoints set up at all major campus entry points. Anyone who is not a student, staff or faculty member will not be permitted on campus and individuals found on campus without a BuffOne ID will be subject to a ticket for trespassing.

Norlin Quad, where the 4/20 smoke out is usually held, will be closed to all people--not just visitors--on April 20, and in order to make it clear that no one is welcome on the Norlin lawn, a fish-based fertilizer will be dispersed over the quad that day, The Denver Post reports.

It's not clear if the campus lockdown will be enough to snuff out the 4/20 mass pot smoking celebration which has become a Boulder tradition and in recent years has gathered more than 10,000 people to Norlin Quad. The Daily Camera reports that Occupy Boulder is already planning a protest in response to CU-Boulder's efforts to stop the event.

According to Occupy Boulder's Facebook page, the protesters plan to "meet, march, [and] smoke." The march will begin at Broadway and Canyon and the protesters will march to, but not on CU campus. Occupy Boulder is inviting all involved to smoke pot at the park near Broadway and Canyon as an act of protest against the crackdown.

WATCH CU-Boulder's 4/20 gathering from 2010 in time-lapse above, more photos and videos below