As America's multibillion dollar cannabis industry continues to expand, the nation's drug cops are seizing less weed.

In 2009, the first summer of Barack Obama's presidency, a record 10.4 million marijuana plants were eliminated in America, according to the federal Drug Enforcement Administration.

California alone accounted for 7.5 million plants that year, according to the DEA's annual report on its "Domestic Cannabis Eradication/Suppression Program," one of the biggest multi-agency law enforcement efforts in the country.

It was also a record year for the California Department of Justice's own Campaign Against Marijuana Planting — CAMP, as it is known and cursed throughout the state's pot-producing regions. Helicopter-riding police associated with CAMP accounted for 4,463,917 plants destroyed, the highest in CAMP's 31-year history. (The DEA total likely includes CAMP's number, though a spokeswoman for Attorney General Kamala Harris was unable to confirm this by press deadline).

Five years later, with recreational cannabis legal in...