'Nothing changes,' U.S. border patrol emphasize you can't cross with pot

You cannot cross the border with pot.

That point was emphasized on legalization day by U.S. Customs and Border Protection (CBP).

"Federal law supersedes state law," said Christopher Perry, director of field operations for the state of Michigan.

The U.S. federal law considers marijuana to be a controlled substance like heroin. So even if pot becomes legal in Michigan next month, travellers need to make sure they and their cars are clean.

"What we're doing today is exactly the same as what we did yesterday," said Perry, "Nothing changes."

Travellers who appear to be violating the federal law with regards to substance abuse would not be admissible into the U.S.

Even though there may be additional inspections at the border, Perry said they are not expecting negative impacts with regard to flow of traffic.

There also wouldn't be any changes to the line of questioning used by border patrol officers. Currently they are"generally are not asking routine questions about people's marijuana use," said Perry.

If travellers are honest about their marijuana consumption, whether they would be rejected at the border will be on a case-by-case basis.

Aside from travellers, those going to the U.S. to facilitate or develop themarijuana industry would generally be deemed inadmissible.

However, if they work in the industry but are going for unrelated purposes, they would generally be deemed admissible.