America's northern neighbor plans to legalize recreational marijuana by July 2018. The government's proposal would permit small marijuana possession at the age of 18 and allows provinces to determine regulations on distribution and vendors. Some marijuana growers in Canada are excited to corner the market legally. Opponents in the U.S. worry about border control, as the bill applies to non-Canadians and could attract American citizens. USA Today says, "Bringing marijuana products across the border could cause confusion for citizens of both countries: Americans who may cross back into the U.S. still under the influence, and Canadians who enter the U.S. unwittingly in possession of marijuana." What are your thoughts?
Sources:
https://www.nytimes.com/2017/08/24/opinion/canada-legalize-marijuana.html?mcubz=3

I still don't understand, whats the strongest argument the US has against the legalization of marijuana?
Members of the DEA still believe marijuana is a gateway drug and think prohibition was effective.
Source: http://www.huffingtonpost.com/2014/10/23/dea-controversies_n_5992324.html
And in reality, this "gateway drug" line was used as an excuse to instagate the War on Drugs, which in turn propagated racial stigmas and stereotypes against black people.