Attorney General Jeff Sessions, the persistent enemy of cannabis legalization, recently sent letters to the first four canna-legal states challenging their oversight of legal marijuana. Washington, Oregon, and Alaska responded with letters in their own defense, and Colorado joined these states this week in hitting back with a letter strongly defending their own cannabis regulation.

Governor John Hickenlooper and Attorney General Cynthia Coffman sent the letter to Sessions on Thursday, noting that their regulations are effective in preventing diversion of Colorado-grown weed to other states. “The State of Colorado has worked diligently to implement the will of our citizens and build a comprehensive regulatory and enforcement system that prioritizes public safety and public health,” the letter states.

“When abuses and unintended consequences materialize, the state has acted quickly to address any resulting harms,” the letter continues. “While our system has proven to be effective, we are constantly evaluating and seeking to strengthen our approach to regulation and enforcement.”

Last month, Sessions told Colorado officials that a 2016 law enforcement report “raises serious questions about the efficacy of marijuana ‘regulatory structures’ in your state.” Hickenlooper responded with a 140-page report collating data from six state agencies. The data reports that the state saw no increase in youth drug abuse, school dropouts, or juvenile arrests since they legalized cannabis in 2012.

The report also notes that legalization has “facilitated the transfer of hundreds of millions of dollars into the Federal Reserve System that would otherwise exist outside of the nation’s banking system.” The other states that received Sessions' letter also hit back with information detailing how legalization was generating massive tax revenue without creating a measurable increase in crime or health issues.