Canadian law enforcement agencies aren’t the only ones preparing for the coming legalization of recreational marijuana on October 17.

US customs and border agents say they too are preparing for Canada’s legalization of recreational marijuana and cannabis, and are vowing to enforce American federal law along the border that’s shared between the two countries.

“Although medical and recreational marijuana may be legal in some US states and Canada, the sale, possession, production and distribution of marijuana all remain illegal under US federal law,” Customs and Border Protection (CBP) officials said in a television interview with Detroit station Local 4 News.

The officials said that anyone attempting to enter the US with cannabis may have the products seized, as well as face fines and possible detention. However, these measures may be short lived in the border city of Detroit, Michigan.

Just after Canada officially legalizes marijuana and cannabis in October, people within the State of Michigan will vote on a ballot measure to also legalize marijuana. The move is widely expected to pass, meaning recreational pot will become legal on both sides of the Ontario-Michigan border — site of the busiest border crossing between the US and Canada.

Other border states such as Washington, Vermont, and Maine have already moved to legalize marijuana, meaning that they will be in the same boat.

Drew Dilkens, Mayor of Windsor (a Canadian border city directly across from Detroit) told Local 4 News that there are some concerns about travelers between Canada and the US not understanding what is legal and illegal with respect to marijuana and cannabis.

“We want to make sure that people who come here don’t have a bad experience and that they’re fully informed when they cross the border that the laws are different here,” he told the television station.

Still, the US border is controlled by federal agents who enforce federal not state law, and marijuana products remain illegal at the federal level in the US, meaning that no marijuana or cannabis products will be allowed to cross between the two countries say US Customs officials.

“This bright red line at the border is something we all need to consider, because federal law will apply at the border, notwithstanding what’s legal or not in either province or state on the other side of that border,” Mayor Dilkens stressed during his interview.

Following the decision by Canada’s federal government to fully legalize cannabis and marijuana throughout the entire country, immigration lawyer Len Saunders told Canada’s CTV News that Canadians who admit to having used the recreational drug at some point in their lives could face a lifetime ban from entering the United States.

To date, nine US states have legalized marijuana for recreational use. However, many legal businesses continue to face challenges to distributing marijuana and cannabis products due to federal prohibitions on the drug. Currently, 31 states have approved cannabis for medicinal use, with another dozen states allowing the drug’s use for some medical conditions and not others.

Several states, in addition to Michigan, have ballot measures coming up this year to legalize recreational marijuana use. Legalization also enjoys bipartisan support among voters, with 62% of Republicans younger than 40 years old support ending prohibitions on marijuana consumption, according to a recent Pew Research poll. Among Democrats, the percentage is 69%, and among independents it’s 65%. Overall, 61% of Americans are estimated to support the full legalization of marijuana.