Personally, I would prefer that the meth-makers and the meth-users be left alone to make and use their crap. Then there would be fewer makers and users to make and use it.
While I agree in general about leaving x-users and x-makers alone, meth is a special case due to the huge hazardous materials issues the meth labs cause.
Actually, even if meth was legal, it doesn't mean you can't protect the public from improper use of hazardous materials.
Use and handling of chemicals hazardous to the public are still regulated and those regulations should be adhered to and enforced.
Lots of companies safely use hazardous materials in the creation of products.
When things are visible, they can be regulated and monitored. When they are forced underground, anything goes.
-john