If the laws allow for prescribed medicinal marijuana, then I would see that as an exception.

I don't understand why you think it is OK for someone that wants a job to be drug tested, but for someone that is not employed and wants/needs to apply for welfare the subject of drug testing is unapproachable and a risk to everyone's liberty.
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A veteran - whether active duty, retired, or national guard or reserve - is someone who, at one point, wrote a blank check made payable to "The United States of America," for an amount of "up to and including my life."