SACRAMENTO, Calif. — In 2010, as Colorado lawmakers were creating America’s first state-licensed and regulated medical marijuana industry, fellow police officers at a Colorado Drug Investigators Association conference jeered a state law enforcement official assigned to draft the legislation.

Some of the sharpest barbs came from visiting narcotics officers from California.

“I was told that we hadn’t learned anything from California — that you can’t do anything to regulate marijuana,” said Matt Cook, a retired Colorado Springs police officer who became the first director of Colorado’s Marijuana Enforcement Division, a policing agency that now regulates state-licensed marijuana workers, pot stores and commercial cannabis producers.

While Colorado moved forward with pot industry oversight, the narcotics officers who berated Cook were right — at least about California, where trying to regulate America’s largest marijuana economy has become a perennial political loser. A key factor has been intense law enforcement opposition itself.

In California, police have forcefully opposed any legislation seen as legitimizing a marijuana industry. Their opposition reflects a belief by many police officers that medical marijuana businesses are profiteering shams that were never authorized by California voters.

Training seminars offered for police by the California Narcotic Officers’ Association suggest there is no such thing as medical […]