> The scary thing is that if you are tested positive I believe you would end up in jail for a month before getting deported, even if you consumed legal drugs in your country (ie cannabis)

This would probably happen in many countries. If I were to smoke cannabis legally and this showed up in a drug test in the US (e.g. stopped while driving) you could also be arrested as a foreigner. With many drugs the effects are not as clear as with alcohol, a test can show up positive even though effects are long gone.