Montpelier — A bill that would legalize adult possession of limited amounts of marijuana is heading to the House floor.

The House Judiciary Committee advanced the measure, H.170, by a vote of 8 to 3 on Wednesday. The vote came after the bill missed a key legislative deadline on Friday, amid speculation that the proposal may not have sufficient support to pass the full body.

The legislation would remove all civil and criminal penalties for adult possession of up to an ounce of pot. It also would allow Vermonters to have up to two mature marijuana plants and four immature plants. Under current law, possession of up to an ounce is punishable by a civil fine.

The proposal does not create a regulated market involving legal sales and taxation — a model implemented in Colorado and other states. Instead, the model would resemble the legal pot system in place in Washington, D.C.

Rep. Maxine Grad, D-Moretown, chairwoman of the committee and a co-sponsor of the bill, asked for her fellow lawmakers’ support before the committee vote.

“This really is a criminal justice issue,” Grad said.

She said she has been troubled by a disparity in penalties for possession of marijuana in different forms: Under the state’s decriminalization law, having small amounts of dry pot brings a civil fine, while possession of plants earns criminal penalties.

One year ago, when the committee voted on a Senate bill that would have legalized marijuana, Grad had reservations. “For me a lot has changed in the last year,” she told the committee on Wednesday.

She said she’s learned more about the issue, which has encouraged her to support this proposal. She cited youth prevention efforts by the Vermont Health Department and an increase in law enforcement officers trained to recognize drug-impaired drivers.

Pending legalization in the nearby states of Maine and Massachusetts is another factor that supports the change in Vermont’s law, Grad said.

Grad addressed uncertainty over the future of the federal government’s stance on state-level marijuana legalization. The more limited proposal is less likely to be in “jeopardy” should the federal government shift from the Obama-era approach of largely leaving it up to states, she said.

“I also do know that just this one incremental step is much safer because it is within our state’s prerogative of defining criminal penalties, different from a tax and regulated system,” Grad said.

Grad said she expects the bill will have support to pass the full House. The measure likely will come up for a vote early next week. If it passes, it would then go to the Senate.

Rep. Chip Conquest, D-Wells River, vice chairman of the committee and a co-sponsor of the bill, said he has concerns about a tax-and-regulate model. He said the bill is the “right policy for Vermont right now.”

The third co-sponsor, Rep. Tom Burditt, R-West Rutland, the committee’s ranking member, described himself as “fairly libertarian.”

“I like this bill. There is minimal government intervention,” he said. He said his support for the measure was bolstered by testimony from a witness from Washington, D.C.

Three representatives on the 11-member panel voted against the measure, including Rep. Janssen Willhoit, R-St. Johnsbury. He raised concerns that without creating a system of regulation and taxation, the proposal will require Vermonters to get marijuana either by growing it themselves or going to the black market.

“That just leaves this big hole that I just don’t think is right to do,” Willhoit said. “Because of that, even though I appreciate the work we’re doing, I’m not going to be able to support (the bill).”

In addition to legalizing small amounts of marijuana, the bill adjusts penalties for possession of larger amounts. Possession of between 1 and 2 ounces or three mature plants would be decriminalized, subject only to a civil fine. Criminal penalties would apply for greater amounts.

The bill missed a Friday deadline by which legislation is expected to emerge from committee, but it was granted an extension.

Sen. Dick Sears, D-Bennington, said he was pleased the House committee was able to meet the extended deadline for the bill to cross over to the Senate.

Sears was a key supporter of a bill last year that would have created a taxed and regulated market. He indicated that proposal might be under consideration again should H.170 pass the House and make it to the Senate Judiciary Committee, which he chairs.

“I’ve heard a lot of folks who are very interested in seeing a regulated system in the House, and it’s no secret that we in the Senate would prefer a regulated system,” Sears said.

“As long as we create a path toward a regulated system that could coincide with Massachusetts’ implementation and Maine’s implementation, I think we’d be in good shape,” Sears said.

Should the bill clear both legislative chambers, it could still face a steep hurdle. Gov. Phil Scott has said he is not opposed to legalization but would like to see a roadside test similar to those used to test for alcohol impairment.