Alaska along with three other western states on Monday asked the Trump administration not to scrap federal policies which have acted as the basis for state cannabis industries.

Existing federal policy is “vital to maintaining control over marijuana in our states” says a letter dated April 3, signed by Gov. Bill Walker and the governors of Oregon, Washington and Colorado. All four states have controlled commercial cannabis industries.

“We request the Trump Administration to interact with us before embarking on any changes,” the letter says.

The letter is addressed to Treasury Secretary Steve Mnuchin and Attorney General Jeff Sessions of the U.S. Justice Department. Sessions was vocal about his opposition to legal marijuana while a part of the U.S. Senate.

“We understand you and others in the administration have some concerns regarding marijuana,” says the letter. “We sympathize, as many of us expressed apprehensions before our states enacted current laws. As governors, we’ve dedicated to implementing the will of our citizens.”

The letter points to two pieces of federal guidance the marijuana industry and state regulators rely on: The Cole Memorandum, and guidance to banks from the Financial Crimes Enforcement Network.

The 2013 Cole Memo is a four-page file from the U.S. Department of Justice that summarizes federal precedence for marijuana enforcement. It records eight distinct scenarios with which the federal government is very concerned, like preventing weed from getting into the hands of minors, and preventing driving under the influence.

The regulators in Alaska often invoke the memo when attempting determine state regulations, considering whether possible rules might make ripples on the federal level.

The Cole Memo is “indispensable” and supplies the basis for state laws, the letter says.

“Changes that damage the regulated market would redirect present marijuana product into the black market and increase dangerous activity in both our states as well as our neighboring states,” the letter says.

The next group of guidelines concern banking. In 2014, the Department of the Treasury Financial Crimes Enforcement Network released guidance for financial institutions trying to provide services for marijuana businesses. It requires vigilant observation, and there are three distinct degrees of reporting banks as well as credit unions have to follow.

Without guidance, financial institutions would be less willing to supply banking for marijuana businesses, compelling those businesses to rely more on cash and raising security hazards.

In Alaska, banks have said they’re staying out of the industry, although their state taxes were paid by about half of marijuana cultivators using a check or a cashier’s check last February.

Gov. Walker opposed Alaska’s initiative that legalized commercial marijuana in November 2014. His representative, Katie Marquette, wrote Monday that he was “upholding the will of the people” with his support in the letter.

Walker joins two of Alaska’s federal lawmakers who’ve also waded into cannabis concerns.

In March, Sen. Lisa Murkowski, who also opposed Alaska’s initiative to legalize marijuana, and Massachusetts Democrat Elizabeth Warren wrote a letter to Sessions asking for clarification on marijuana laws.

Meanwhile, Rep. Don Young has joined the recently formed Cannabis Caucus, vowing to pursue changes to banking and other federal laws regarding marijuana. Young, who has said he does not condone marijuana use but that it should be left up to the states, has said he wants to “educate” the administration on impacts of legalized marijuana.

Twenty-eight states as well as the District of Columbia have medical marijuana programs. Eights states along with the District of Columbia have legalized adult recreational use.