The memo refers to the 1970 Controlled Substances Act, where cannabis is classified as a drug in the same category as heroin.
Gardner, who was in the Fort Collins area touring local businesses Friday, said he felt misled by Sessions on federal marijuana policy and that Sessions' decision Thursday to rescind the so-called Cole memo took him by surprise.
"The previous issuance of guidance undermines the rule of law and the ability of our local, state, tribal, and federal law enforcement partners to carry out this mission", wrote Sessions, according to NBC.
It's not clear what impact the change will have or whether federal prosecutions of marijuana cultivation or sales will increase, but the change makes prosecution easier.
James Dunn covers technology, biotech, law, the food industry, and banking and finance.
"This extremely misguided action will enable a federal crackdown on states' rights with regard to marijuana policy", said Matthew Schweich, interim head of the Marijuana Policy Project.
The decision, which rescinds previous marijuana prosecution policies, comes just days after the State of California began legal recreation sales of marijuana on January 1.
"In the short term, this news will further scare away investors, which will, in turn, slow down cannabis entrepreneurship", said Nicolas Ruiz, co-founder of Cloudponics, a San Francisco startup whose technology can be used to grow marijuana. They had closed down several hundred before Congress intervened with budget restrictions that halted the lawsuits - one of them targeting Harborside Health Center in Oakland, the nation's largest licensed cannabis dispensary - as well as most federal criminal prosecutions.More news: Spurs can not force Harry Kane to stay, admits Pochettino
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Back in 2013, as an increasing number of states began to legalize marijuana, Cole released a directive to federal prosecutors that essentially adopted a policy of non-interference with marijuana-friendly state laws. The memo discouraged prosecutors from going after people participating in the marijuana trade in states where recreational marijuana is legal, except in cases with aggravating factors.
Robert Troyer, who was appointed an interim US attorney for the District of Colorado by Sessions in November, said his office's decisions regarding marijuana cases would be guided by similar principles as before: "focusing in particular on identifying and prosecuting those who create the greatest safety threats to our communities around the state".
The immediate reaction to Thursday's news from the marijuana industry and some members of Congress was alarm.
Rep. Earl Blumenauer, an Oregon Democrat and co-chairman of the Congressional Cannabis Caucus, called Sessions' decision "outrageous". "California voters made a decision to legalize adult use of cannabis in 2016".
Democratic Congresswoman Dina Titus wishes to see legal marijuana continue to flourish.
Los Angeles City Council President Herb Wesson Thursday criticized the Trump administration's announcement that it is rescinding a federal policy providing legal protection for marijuana sales in states with recreational pot.
However, Jeff Sessions' stand point is strictly speaking correct.
Under the state's medical marijuana law enacted in 2014, NY has 1,384 medical practitioners and 40,286 certified patients. "Once again the Trump administration is doubling down on protecting states' rights only when they believe the state is right", Wyden said in a statement. The open question is how broadly or narrowly that appropriations rider may be interpreted down the line, as it is an unsettled issue in the federal courts.