"Republican Sen. Mike Enzi does not support the bill because he has strong reservations about marijuana for medical use, said his spokesman Max D'Onofrio."

"There is strong evidence that marijuana does act as a gateway drug, and Sen. Enzi believes we must think about what kind of message these laws would send to our young people," D'Onofrio said in an email. "There is also no clear science-based evidence that medical marijuana is more effective than other regulated medicines. Approval of medical marijuana use at this time is premature until the research is more conclusive about benefits and risk."
3/14/15
http://trib.com/news/state-and-regional/govt-and-politics/wyoming-s-senators-oppose-medical-marijuana-bill-in-congress/article_adedce3d-41c3-5827-be5d-5c8f4c908985.html