Later this year Marijuana-Cannabis will become legal for recreational use, and has already been legal for quite some time for medical reasons.
If you are planning to cross the border, please refrain from bringing your pot-weeds across the border with you, as it is still illegal in the USA on a federal level.
If you get busted at the border with the green leafy buds, you can face a fine, or be held in custody with a pending penalty which could be jail time.
Border guards will continue to enforce their laws. Keep your cannabis products at home.