Coloradans voted to legalize marijuana in November 2012 and pot-related arrests plummeted in 2013. Despite the decline, more than 1,000 people were charged in Colorado last year with possession of less than 2 ounces of the drug.

Voter-approved Amendment 64 legalized possession of 1 ounce of marijuana, effective Dec. 10, 2012, for adults over age 21. Residents can legally grow six plants and gift 1 ounce to friends. Medical marijuana patients can possess 2 ounces.

A year-to-year comparison of marijuana-related charges in the first nine months of 2012 and 2013 was reported Sunday by The Denver Post, which acquired the data from the Colorado Judicial Branch.

Between January and September 2013, 1,194 people were charged in Colorado with possession of less than 2 ounces of marijuana, a misdemeanor. During the same period a year earlier, 6,422 people were charged with petty possession, meaning charges for that offense declined by 81 percent.

It's unclear, however, why there remained a substantial number of busts for small-scale possession.

Many, but not all, of the petty possession charges listed in a spreadsheet of cases from the Colorado Judicial Branch were filed against adults between the ages of 18 and 21. Some of the charges were filed against juveniles and some against adults over 21.

Rachel Gillette, executive director of Colorado NORML – a chapter of the National Organization for the Reform of Marijuana Laws – says charges for possession of less than 2 ounces may in part "be the result of confusion about the law by some people." For more than a decade, she notes, Colorado has permitted medical marijuana patients to possess 2 ounces.

"Generally we're very pleased" with changes to policing, she says. The group currently is more focused on the state's drugged driving law and working to limit the possibility of felony charges for residents exceeding the law's allowable possession and plant limits.

Although the advocacy group's board hasn't discussed a position on legalization for 18- to 21-year-olds, Gillette believes "there's no reason we should be ruining a young person's life because they are possessing some amount of marijuana."

Diane Goldstein, a board member of Law Enforcement Against Prohibition, says it's possible some police officers are "intentionally undermining the law" by using their discretion to make arrests.

"The problem with statistics is you lose the context of the arrest," Goldstein says. "Police have a wide latitude in discretion."

Goldstein, a retired police lieutenant commander from Redondo Beach, Calif., points out that judges dismissed 84 percent of petty possession charges filed during the month of September 2013, which she sees as a sign cops also may not have received proper training on implementing the law. In September 2012, the dismissal rate for petty possession was lower, at 79 percent, the Post reports.

Goldstein says some of the charges likely are filed because of probation or parole violations.

The total number of marijuana-related criminal charges in Colorado state courts was 1,674 in the first nine months of 2013. In the same period in 2012, there were 7,274 such charges. The Post reports the number of charges for possessing more than 12 ounces declined 73 percent while the number of charges for possession with intent to distribute less than 5 pounds fell 70 percent. The number of citations for public consumption dropped 17 percent.

State-licensed recreational marijuana stores opened in the state on Jan. 1. Local communities have the power to block stores and the city council of Colorado Springs, the state's second-largest city, voted in July to prevent the opening of one there.

Mason Tvert, co-director of the Amendment 64 campaign and current spokesman of the Marijuana Policy Project, says the significant decline in marijuana charges is evidence that police are properly adjusting to legalization.

"Law enforcement officials surely have better things to do with their time than arresting and prosecuting adults for using a less harmful substance than alcohol," he says. "Adjusting to new laws is not a new concept for police and prosecutors, and it appears they are doing it successfully in this case."