In King County, the decision will impact 175 cases involving individuals age 21 and older accused of possessing one ounce or less of marijuana, said Dan Donohoe, spokesman for the Prosecutor's Office.
With the passage of I-502, marijuana possession of one ounce or less by individuals age 21 and older will become legal in the state on Dec. 6.
King County Prosecuting Attorney Dan Satterberg said that dismissing these cases is the right thing to do in light of Tuesday's vote.
"Although the effective date of I-502 is not until Dec. 6, there is no point in continuing to seek criminal penalties for conduct that will be legal next month," Satterberg said.
Pierce County Prosecutor Mark Lindquist told the Associated Press his office will also be dismissing misdemeanor pot cases involving adults age 21 and over. He didn't have the number of cases affected available.
The prosecutors' decisions are the latest signal that law enforcement authorities already are taking a very different approach to marijuana cases in response to the legalization initiative.
Cosmopolis Police Chief Casey Stratton says his department has suspended its work on an investigation that would have been considered a large marijuana bust, prior to the passage of Initiative 502.
Stratton said he's asking the Grays Harbor County prosecutor for guidance and waiting for more federal response to the law decriminalizing the possession of up to an ounce of marijuana.
In addition, Seattle police said Friday they will no longer assist federal authorities in investigations of marijuana users or marijuana-related businesses that are legal, at the state level, under I-502.