A sign is shown by the entrance of a medical marijuana clinic in Las Vegas

 
A sign is shown by the entrance of a medical marijuana clinic in Las Vegas
A sign is shown by the entrance of a medical marijuana clinic in Las Vegas, Nevada, September 8, 2010. Authorities say police and federal agents are serving search warrants at several locations in an investigation of medical marijuana clinics in and around Las Vegas. REUTERS/Las Vegas Sun/Steve Marcus (UNITED STATES - Tags: CRIME LAW HEALTH SOCIETY)