U.S. Senator Catherine Cortez Masto, D-Nev. was one of 11 U.S. senators to co-sign a letter Thursday asking the Department of Justice to uphold the guidance on state marijuana laws that has been in place since 2013.

The letter is addressed to U.S. Attorney General Jeff Sessions, who stated this week that he is "definitely not a fan of expanded use of marijuana." He added that states can pass laws but consuming and distributing marijuana remained a federal violation.

Only one Republican senator signed the follow-up letter, which is signed by lawmakers from all eight states that have so far legalized recreational marijuana, including Alaska, California, Colorado, Maine, Massachusetts, Nevada, Oregon, and Washington. The District of Columbia also has legalized weed.

“It is essential that states that have implemented any type of practical, effective marijuana policy receive immediate assurance from the DOJ that it will respect the ability of states to enforce thoughtful, sensible drug policies in ways that do not threaten the public's health and safety,” the senators wrote. “This ensures that state infrastructure, including tax revenue, small businesses, and jobs, can be protected; DOJ resources can be used most effectively; and most importantly, that marijuana can be properly regulated to improve public health and safety.”

Senators that signed the letter included Cortez Masto, Elizabeth Warren, D-Mass., Lisa Murkowski, R-Alaska, Patty Murray, D-Wash., Ron Wyden, D-Ore., Jeff Merkley, D-Ore., Maria Cantwell, D-Wash., Ed Markey, D-Mass., Brian Schatz, D-Hawaii, Cory Booker, D-N.J. and Michael Bennet, D-Colo.

The letter was initially prompted by White House Press Secretary Sean Spicer's remarks during his briefing on February 23rd, suggesting that the public would soon see “greater enforcement” against any state that has legalized use of the drug.

"On the campaign trail, then-candidate Trump stated that despite his personal views regarding marijuana use, legalization should be left to the states. 3 Last week Mr. Spicer suggested that while President Trump supports medical marijuana, there is 'a big difference between that and recreational marijuana,' alleging that medical marijuana states 'have set forth a process to administer and regulate' that usage. Mr. Spicer also stated that he believed the public would see 'greater enforcement' of federal marijuana laws," senators said. 

Guidance issued by the Department of Justice in 2013, known as the “Cole Memorandum,” provides an outline of the interaction of state and federal laws regarding marijuana use. According to the memorandum, enforcement of marijuana-related activities should be addressed primarily by state regulatory bodies and local law enforcement in states with “strong and effective regulatory systems” already in place.

Spicer noted that the department would not go after the medical marijuana industry. Twenty-eight states have medical marijuana laws, and 21 states have decriminalized the use of marijuana.

Already, there are indicators that Spicer's comments were genuine.

On Monday, the Office of the Attorney General in Nevada confirmed that U.S. Attorney Daniel Bogden had warned the Moapa Paiute Tribe outside of Las Vegas that the tribe was not allowed to have cannabis on site at a cannabis-centric event scheduled for this weekend, March 4-5. The event, the 2017 High Times Cannabis Cup, is one of the largest marijuana conventions in the world and draws thousands of people.

The tribe still is working with the U.S. Attorney's office to sort out the matter in a way that works for federal, state and tribal officials.