Decriminalize is something different. You mean legalize and regulate (like cigarettes and alcohol).
If drugs are legal, would you allow people to make their own -- like marijuana, methamphetamine, and crack cocaine? How will you tax that effectively -- or would you just let that go untaxed?
What's to stop the gangs from going into the export business, legally growing and manufacturing cheap drugs here in the U.S. and illegally shipping them to countries where drugs remain illegal?
Currently, government taxes on cigarettes (federal, state, county, and city) are driving that product underground. But that won't happen with drugs?
Let's go back to Prohibition. This was a miserable failure.
The drug war is following the same path. Lots of crime. Lots of dead folks. A few folks getting filthy rich.