Beginning Friday, possession of less than one ounce of marijuana in Massachusetts will become a civil offense instead of a criminal offense.
Law enforcers can issue citations for $100.
Auburn police Chief Andrew Sluckis says his department makes several marijuana-related arrests each week.
But the law is about to change in the new year when the ballot initiative known as Question 2 takes effect.
"I think given the way the fine structures are set up now there's absolutely no incentive for people not to carry less than an ounce of marijuana," Sluckis said. "And there's little incentive for police to enforce the law."
Sluckis and some other police chiefs say there's no mechanism in the law to make violators identify themselves -- and no way to force people to pay the fine.
When it comes to issuing the citation, Chief Sluckis and others told WBZ-TV the form doesn't exist.
Sluckis said officers won't be able to write a ticket to those in violation of the new pot law.
"Nor am I planning to get the ability to do that," he said.
Public Safety and Security Secretary Kevin Burke says the state is recommending communities pass their own ordinances against public pot smoking.
Juveniles caught with under an ounce are supposed to undergo drug education.
But Burke explains that there currently isn't a program to refer people to.
He says a variety of state agencies are working to develop that program, which is required by the new law. But there is little money and no timetable for the program.
Police chiefs in Bristol County met Tuesday to discuss enforcing the new law. Massachusetts is the 13th state to decriminalize small quantities of marijuana. The ballot measure was passed with the approval of 65 percent of voters.