Airport officials, for the most part, have bigger issues to deal with than marijuana. “The people who drink alcohol, a lot of times are aggressive, but if they come in stoned, they’re much more mellow,” said Brian Kulpin, a Reno airport spokesman. “A lot of times, they’re apologetic.”

Denver has more trouble with people trying to bring water bottles through security lines than marijuana, airport spokeswoman Stacey Stegman said.

Earlier this month, Canada became only the second country to legalize recreational pot nationally. The change prompted both U.S. and Canadian governments to issue travel reminders about U.S. marijuana laws.

“If a traveler is found to be coming to the U.S. for reason related to the marijuana industry, they may be deemed inadmissible,” Customs and Border Protection said in a statement on Canada’s pot change. Those who work in the industry but are visiting the U.S. for a reason unrelated to their business “will generally be admissible to the U.S.” The agency leaves such decisions to the discretion of CBP officers, which could pose some tricky questions for travelers quizzed about their employment, lawyers note.

“I would say, as a general matter: Tell the truth, but answer questions like you’re in a deposition. Answer the question truthfully and narrowly,” said Stanley Jutkowitz, a Washington attorney who runs the cannabis practice at Seyfarth Shaw.

Traveling with marijuana, or working in the industry, could also be grounds for removal from the TSA’s PreCheck or other U.S. Trusted Traveler programs aimed at speeding a traveler’s return into the country.

The U.S. Trusted Traveler programs have 8 million members, including 5.6 million for the Global Entry program as of Aug. 31, according to Customs and Border Protection. The agency declined to reveal how many Trusted Traveler privileges it has revoked and denied overall in recent years. An Oct. 15 request for that data by Bloomberg News under the Freedom of Information Act remains pending.

“As marijuana remains an illegal drug in the U.S., the use of it or involvement in the industry could make a person ineligible for Trusted Traveler membership,” CBP spokeswoman Stephanie Malin said in an email.

U.S. law enforcement has long grappled with how to approach marijuana. The Justice Department notified prosecutors in 2013 that medical and personal possession of marijuana didn’t merit bringing federal cases. In January, then-U.S. Attorney General Jeff Sessions rescinded that notice, known as the Cole Memo, and left the matter largely to local prosecutors’ discretion. In practice, the outcome largely depends on the quantity of marijuana and the jurisdiction in which it is detected. In many places, a gram or so probably won’t raise eyebrows. A large suitcase packed with weed is likely to launch a state or federal prosecution.

Ultimately, changes at the federal level will be required to resolve the mess of U.S. marijuana rules, lawyers said. The Strengthening the Tenth Amendment Through Entrusting States Act, known as the STATES Act, is currently pending in Congress. The bill would exempt people and companies in states that have legalized marijuana from federal prosecution of marijuana under the U.S. Controlled Substances Act, leaving pot enforcement to the states. In June, a dozen governors, including four Republicans, wrote to congressional leaders seeking their support for the bill, which has both House and Senate versions. “The STATES Act is not about whether marijuana should be legal or illegal; it is about respecting the authority of states to act, lead and respond to the evolving needs and attitudes of their citizens,” the governors wrote.