Activists who worked to legalize marijuana last year say the bill the House is expected to vote on Thursday to change the ballot law is an insult to the voters and will allow the illicit black market to thrive. The Marijuana Policy Committee meets at noon Wednesday to vote on the marijuana bill that is expected to go before the full House on Thursday.

The bill would allow a board of selectmen or city council to approve a ban on retail marijuana sales rather than require a community-wide referendum, as is required under the ballot law, and would raise the tax on retail marijuana from a maximum of 12 percent to as much as 28 percent.

"The House proposal in no way improves the measure passed by voters. It weakens it and it insults voters in the process," Jim Borghesani, spokesman for the Yes on 4 campaign and the Marijuana Policy Project, said in a statement. "Its irrational tax increase will give drug dealers the ability to undercut the legal market, and its removal of ban authority from local voters will give a handful of selectmen the ability to overrule the opinion of their own constituents."

Borghesani and Yes on 4 Coalition political director Will Luzier plan to hold a press conference outside Hearing Room A-1 in the State House immediately after the Marijuana Policy Committee meets to vote on the House proposal. Peter Bernard, president of the Massachusetts Grower Advocacy Council, emailed all members of the Marijuana Policy Committee on Wednesday morning and told them the House proposal "may as well have repealed Question 4."

"You guys screwed the pooch," he wrote in the email. "A 28% tax rate? 10mg edible limits? Letting towns opt out without a constituent vote? You may as well have repealed Question 4. These three things are incredibly huge gifts to the black market. We thought you wanted to damage or eliminate the black market, but instead you gave them reason to celebrate. It is as though someone wants the black market to continue to thrive, because that's what these measures do."