One of the world’s largest marijuana festivals, which is expected to be held this week on tribal land outside of Las Vegas, has been facing a possible shutdown for the past two weeks, according to a letter sent by federal officials earlier this month.

U.S. Attorney Daniel Bogden, based in Las Vegas, sent a Feb. 16 letter to the Moapa Paiute Tribe reminding the tribe that the transport, possession, use and distribution of marijuana is illegal under federal law. The marijuana trade show and festival, planned for March 4 and 5, would be in violation of that law, according to the letter obtained by the Reno Gazette-Journal.

“I am informed that the tribal council is moving forward with the planned marijuana event referred to as the 2017 High Times Cannabis Cup because it is under the impression that the so-called ‘Cole Memorandum’ and subsequent memoranda from the Department of Justice permit marijuana use, possession and distribution on tribal lands when the state law also permits it. Unfortunately, this is an incorrect interpretation of the Department’s position on this issue.” [Read more at Reno-Gazette Journal]