The war on murder has been going on for millennia, and we *still* have not won it. Maybe it’s time we gave up on that one, too.
Oh, wait a minute. We *did* give up in the war on murder with respect to a certain class of victims. When we did that, the murder rate of unborn children skyrocketed from fewer than 10,000 per year to over 1.6 million per year in just a few years, and is currently around 800,000 per year. Yep, giving up that particular fight sure had positive results.
It is impossible to eliminate any kind of criminality. The best we can do is control it and reduce its incidence by making and enforcing laws against it. If your standard is that laws must completely eliminate criminal activity or be thrown out, then we will have no laws and civilization becomes impossible.
There is no sound evidence that laws against marijuana reduce its incidence to any substantial degree. And while the FBI reports that 2 in 3 murders are solved, assuredly no more than 2 of 3,000 marijuana "crimes" even come to the attention of law enforcement - which is to be expected, because while murder has a victim, every participant in a marijuana "crime" wants it to succeed and go undetected.
Drugs are a commodity, murder isn’t. So let’s continue to keep it illegal and the criminal elements prospers. Drugs dealers don’t ask for id. Ever consider that?