Well where I live it's legar for the purposes I use it for. Mainly pain relief, counteracting some of my weakness (don't realize how weak I am when I'm high), and controlling my muscle spasms. It's also been proven in multiple studies to be one of the most effective drugs on the market (when smoked) for controlling chronic vomiting and nausea. Also, it's available in a refined pill form for those (with the cash) who want to avoid the negative aspects of smoking.
Also, marijuana is a habit
forming drug, where as certain pain killers and muscle relaxants which could be used as alternatives are highly addictive, not to mention have side effects of reducing one's appetite, vomiting and nausea, etc.
It's not a matter of druggies using medicinal marijuana as an excuse to get their fix; it's a legitimate medicinal drug that's been in use for thousands of years.
For more infromation, feel free to check out the Wikipedia articles on Cannabis
and Medicinal Marijuana