Shares of marijuana-related companies tumbled Thursday on a report that Attorney General Jeff Sessions is planning on ending a policy that allowed pot legalization to thrive.

NBC News' Pete Williams confirmed Sessions made the decision to rescind an Obama administration 2013 memo, which stated it would not stand in the way of states that legalize marijuana in most cases. The Associated Press was the first to report the news.

Shares of Scotts Miracle-Gro, which has been a Wall Street favorite because of potential for increased fertilizer and equipment sales related to legal marijuana crops, dropped 7 percent on Wednesday.

ETFMG Alternative Harvest ETF, an exchange-traded fund which just recently changed its focus to marijuana-related investments, fell 9 percent.

One Wall Street analyst downplayed the impact of the decision, saying the legalization movement won't be affected.

"We don't view this as terribly disruptive, as enforcement decisions will seemingly be left to state-level AG's," Cowen analyst Vivien Azer wrote Thursday. "In legal adult use cannabis states, given the tax revenue generation, we believe local governments and AG's are largely on-board with legalization."