A company has bought a town in California and plans to develop it into a marijuana tourism destination. Above picture shows people looking at jars of marijuana at the medical marijuana farmers market at the California Heritage Market in Los Angeles, California July 11, 2014. Reuters

Increased enforcement of federal marijuana laws could lead to dangerous and unintended consequences, the governors of four Western states said in a letter to Attorney General Jeff Sessions and Treasury Secretary Steven Mnuchin on Monday.

The governors of the first four states that legalized recreational marijuana use — Alaska, Colorado, Oregon and Washington — sent the letter after the Trump administration signaled it would step up enforcement of federal marijuana laws, which often conflict with state laws. In 2013, the Obama Justice Department issued guidance for federal attorneys called the "Cole Memo" that recommended prosecutors avoid pursuing charges against marijuana users and businesses in states that had legalized the drug.

Read: Trump And Marijuana: Justice Department Contacts Colorado Officials About Cannabis Cases

"We understand you and others in the administration have some concerns regarding marijuana," the governors wrote. "Overhauling the Cole Memo is sure to produce unintended and harmful consequences. Changes that hurt the regulated market would divert existing marijuana product into the black market and increase dangerous activity in both our states and our neighboring states."

The letter was addressed to Sessions, the nation's top law enforcement officer and the person, besides the president, most capable of changing the way the federal government treats the wide discrepancy between federal and state marijuana laws.

"I reject the idea that we’re going to be better placed if we have more marijuana and you can just go down to the corner grocery store and get it—give me a break," Sessions said earlier this month.

Sessions also took aim at drugs altogether. "Our nation needs to say clearly once again that using drugs is bad, that it will destroy your life."

While there have been no official changes to federal enforcement of marijuana laws, the Trump administration has requested information from the states on marijuana cases, indicating changes could be forthcoming.

The letter was also addressed to Mnuchin because the treasury department's Financial Crimes Enforcement Network (FinCEN) issued guidelines similar to the Cole Memo in 2014. The governors warned that any changes to the FinCEN guidance could make the legal marijuana industry more dependent on cash, which would increase "safety risks both to the public and to state regulators conducting enforcement activity."

Eight states and the District of Columbia have voted to legalize recreational marijuana use, and as voters have continued to pass medical marijuana ballot measures, there are now only six states that have not legalized marijuana in some capacity.

Last week, Democratic lawmakers from Oregon introduced legislation to end the divergence between state and federal marijuana laws and set up a framework for the federal regulation of the plant.