A Colorado ballot initiative to legalize limited possession of marijuana for adults is set to pick up an endorsement from a civil rights organization Thursday.

At a morning press event, the head of the Colorado, Wyoming and Montana conference of the National Association for the Advancement of Colored People is expected to announce the conference’s support for the initiative, Amendment 64. The conference’s president, Rosemary Harris Lytle, said Wednesday the endorsement comes not out of an interest in marijuana use but instead from a concern over the lopsided numbers of African-Americans arrested for marijuana offenses.

“In ending the prohibition against adult use of marijuana we might affect mass incarceration and its disproportionate impact on African-Americans and other people of color,” Harris Lytle said.

In 2010, African-Americans accounted for roughly 9 percent of all arrests for marijuana possession in Colorado and 22 percent of arrests for marijuana sales or cultivation, according to figures advocates pulled from FBI data. African-Americans made up about 4 percent of the Colorado population that year.

The local NAACP endorsement follows a similar endorsement by the California NAACP of a marijuana-legalization measure there in 2010. And it is in line with the national NAACP’s stance against the drug war.

“The realization is that drug laws have been disproportionately enforced against communities of color,” said Niaz Kasravi, the national NAACP’s criminal justice director.

Adams County District Attorney Don Quick, who opposes the initiative, agreed that African-Americans are over-represented in the criminal justice system.

“There’s no denying it and that’s wrong,” Quick said. “But the answer to that isn’t to make marijuana more available in the community.”

Quick said a proliferation of marijuana among adults will trickle down to kids, resulting in lower graduation rates and more discipline problems.

Quick said Colorado Department of Corrections figures show that people imprisoned for marijuana crimes make up about 1 percent of inmates.

The Weld County Board of Commissioners on Wednesday passed a resolution opposing the initiative.