HAVERHILL — A lawsuit filed against a business that plans to sell recreational marijuana brought about 20 protesters to Railroad Square late Saturday morning.

They stood across the street from Mark's Deli, whose owner along with two other plaintiffs has challenged the city's decision to allow the opening of a pot shop in the now-vacant quarters of the Sons of Italy at 124 Washington St.

The lawsuit alleges that allowing the shop violates the constitutional rights of nearby property owners, violates federal narcotics laws and is detrimental to Haverhill.

"I believe strongly we need to get the underground economy into the mainstream," said Douglas Edison, a longtime community activist who is running for City Council.

"Why are we stopping it? You can't just say 'no' to everything," he said. Edison pointed out the shop will pay taxes to the city.

"We need money for schools," Edison added. Caroline Pineau, who already owns and operates the Yoga Tree at 90 Washington St., hopes to open the recreational marijuana store.

"I've been fighting for this for 15 years," said Michael Crawford of Marblehead. He called the lawsuit "frivolous."

A friend of his who suffered from mental health problems and addiction had a very positive outcome after he started using medicinal marijuana, Crawford said.

"It turned his life around," he said.

Crawford wore a shirt bearing the message, "more weed, less greed."

Another City Council candidate, Nick Golden, said Pineau is being "unfairly targeted" by the lawsuit.

"She represents the type of person and entrepreneur that we're trying to attract," said Golden, who is on the staff of state Rep. Lori Ehrlich, D-Marblehead.

"I think it's really important to support small business owners," Christina Barbieri, a former Haverhill resident, said.

She and others noted that possession of marijuana is now legal in Massachusetts and that Haverhill voters supported this change.

The protesters held signs with messages such as "drop the lawsuit." Many motorists driving by honked in support of the cause.

A few people voiced their objection to having a pot shop in the city, Crawford said. One man confronted the protesters and called them "immature."

As he walked away from the group, he extended his two middle fingers. Two police officers were assigned to the demonstration, which remained orderly.

Officer James Keenan advised the man who made the obscene gestures to not cause a disturbance.

Jess Hileman, a lifelong Haverhill resident and longtime patron of Mark's Deli, said he does not think the owner of the restaurant objects to having a pot shop in Haverhill.

"He only opposes the location," he said. Hileman also said he did not think it was fair that some of the protesters were depicting the owner as a bad guy.

A patron at Mark's Deli said the owner did not want to speak to the media. The lawsuit lists the plaintiffs as Bradford Brooks, a local realty professional; Lloyd Jennings, a contractor; and Steve Dimakis, owner of Mark's Deli.

Brooks and Jennings are described as trustees of L&B Realty Trust. Dimakis is identified as a trustee of the Evthokia Realty Trust.