Post 9/11 America clamped down on its border security and that meant even us friendly Canadians next door can have significant trouble crossing into the United States.
Credit: politico
Seemingly small details such as having a marijuana possession charge on one's record can lead to access being denied.
Even as some states legalize marijuana it is still illegal at the federal level, which means anyone that has small charges such as myself will most likely be turned around at the border and told to go home.
Ofcourse Canada is all set to legalize pot countrywide but even if you've smoked pot before you could be denied access into the United States as I understand. This is horseshit ofcourse but border guards have alot of power, if they don't want to let you in they can deny you..so it's best to try to make a good impression.
If you get asked by border guards if you smoke weed the best thing to do is lie, tell them you haven't and if you don't have any priors for possession or trafficking you should be all good.
There are pardon services and preclearance waivers you can apply for in Canada to enter the United States, the problem aside from the length of time they take to process and the hundreds of dollars they cost, is that it's still at the discretion of the individual border patrol whether or not you can gain entrance? Hypothetically you can get clearance, book your trip and still be denied at the border which for me is alot of time, effort and money to waste for the chance I could get turned around before I get to my destination. It's just not worth it or the headache.
So until the U.S relaxes its laws 
Thanks for reading,
This guy has even stated publicly that he's smoked pot before but they still let him across the border 😞 you have to know someone I guess?..