Suzanne Kreiter/Globe staff
Representative Ronald Mariano, a Quincy Democrat and the majority leader, spoke about the revisions to the marijuana law on Monday at the State House.
The Massachusetts Legislature is expected to approve a broad overhaul of the voter-approved marijuana legalization law this week, after House and Senate negotiators came to an agreement on Monday that will hike pot taxes, change local pot shop regulation, and maintain the right of adults to consume the drug.
But the compromise immediately raised the specter of a serious legal challenge, and the bill drew a rebuke from the top lobbyist for cities and towns, who said, should it pass, most municipalities would struggle to implement the law.
The bill raises the total tax on retail pot purchases to a maximum of 20 percent, up from a maximum of 12 percent that was spelled out in the ballot law. The legislation would merge oversight of the recreational and medical marijuana industries into a five-person Cannabis Control Commission.
And it would maintain the right of adults 21 and older to