It's not that he can't enter the US. It's just that he has to file an extra form and pay a fee. The legal situation around marijuana in the US sucks. It may

It's not that he can't enter the US. It's just that he has to file an extra form and pay a fee. The legal situation around marijuana in the US sucks. It may be legal at the state level where you live, but it's still very much illegal at the federal level and in theory you can spend a year in federal prison on the first offense for any amount.