You always have the option to leave, unless it's your property in which case you can make them leave.
Besides making drugs illegal has shown time and time again to increase drug use.
See Above.
And legalizing it sure would decrease it?
Also, it's public property, meaning the public has the right to disagree with druggies loving up the place.
Oh, but I guess it's okay to see a bunch of crackheads running around, as long as I don't own the place.