Marijuana smokers pass a bong at the Denver 4/20 pro-marijuana rally at Civic Center Park in Denver on Saturday, April 20, 2013. Authorities generally look the other way at public pot s

 

              Marijuana smokers pass a bong at the Denver 4/20 pro-marijuana rally at Civic Center Park in Denver on Saturday, April 20, 2013. Authorities generally look the other way at public pot s
Marijuana smokers pass a bong at the Denver 4/20 pro-marijuana rally at Civic Center Park in Denver on Saturday, April 20, 2013. Authorities generally look the other way at public pot smoking here on April 20. Police said this week they're focused on crowd security in light of attacks that killed three at the finish line of the Boston Marathon. (AP Photo/Brennan Linsley)