No, obviously not, in fact our drug testings policies would become more similar to ones in places like Canada, where basically they test you not only for drugs but also alcohol in the workplace, but the tests indicate if you are under the influence, not if the drug is simply in your system.

You can't come to work drunk as fuck, can you?

And certain professions could still test for safety reasons, and naturally you'd have to work out insurance logistics.

What's the next question? ZOMG YOU WANT TO MAKE PEOPLE HEROINED-OUT AND METHED-UP ZOMBIES ON THE ROAD? No, DUI would still be illegal, and you'd still be responsible for any criminal actions you committed while under the influence (it could potentially an aggravating circumstance, even).

What we are talking about is the use of the drugs for personal consumption, and the safe manufacture/distribution/sale thereof. That's it. No other straw men.