DENNIS — Families and friends have lolled away long summer days on a secluded off-road beach in East Dennis for generations, driving across the broad tidal flats to bask at the water’s edge.

“It’s the highlight of everybody’s summer,’’ said Justin Labdon, a resident of neighboring Brewster who cherishes motoring across the flats with his children and paddleboards. “My kids call it Adventure Beach.’’

That adventure, which a member of the town’s Conservation Commission called the “pursuit of happiness,’’ might be coming to an end.

Citing concerns over erosion and pollution, state regulators want to ban recreational vehicles from the firm, smooth sand that stretches for more than a quarter-mile into Cape Cod Bay, believed to be one of the last exposed tidal flats open to off-road traffic in Massachusetts.

Beach access is near and dear to Cape residents, and the surprising announcement that driving on the Crowes Pasture flats might be banned has drawn an outcry.

“They will not be happy until every human is kept within their designated ‘appropriate’ areas,’’ groused summer resident John Fitzgerald, a 43-year-old father of two children.

The town’s Conservation Commission, more accustomed to sleepy talk of easements and egress, drew a feisty, standing-room-only crowd to a recent meeting where the chairman seemed as irate as the residents.

“Will you please explain to me what the hell is going on?’’ chairman George Macdonald, who opposes the ban, asked in exasperation to loud applause.

For years, driving on the flats raised no concerns. The state does not have a blanket prohibition on the practice, and in 2004 the state Department of Conservation and Recreation wrote that it recognized the use of recreational off-road vehicles at Crowes Pasture, Macdonald said.

But when the mid-Cape town recently proposed an update to its 1999 beach management plan, state agencies took notice and specifically objected to this traffic on the flats.

In December, the state Department of Environmental Protection notified town officials that the flats should not be used for off-road vehicles because they “may cause compaction of the resources there, and the area may also be impacted by fluids and other contaminants leaking or falling off,’’ said Ed Coletta, a department spokesman.

In early March, state conservation officials weighed in by saying that the “proposal to continue allowing recreational off-road vehicle access to the tidal flats does not further the purposes of the conservation restrictions and should not be allowed.’’

Macdonald said he was blindsided.

No sea life is endangered, because the flats are barren, he said, and other off-road vehicles are allowed to drive to small aquaculture plots on the flats.

“There had been a clear understanding that all of the activities that are currently allowed will be ongoing,’’ said Macdonald, who served as the town’s natural resources director for 33 years. “I’ve told the public many, many times, ‘Don’t worry.’ ’’

At the recent meeting, which the Globe watched later on video, most commissioners questioned why change is needed at the Crowes Pasture Conservation Area.

But even if the panel pushes back, the state can ban vehicles from the flats because of its authority over wetlands protection, according to Karen Johnson, the town’s natural resources director.

The dispute has prompted Dennis to seek legal advice on how to proceed.

All of that is so much bureaucratic mumbo-jumbo for the many families who clamber into Jeeps, four-wheel drive SUVs, and other off-road vehicles to meander along a narrow dirt track and then drive onto the beach near the mouth of Quivett Creek.

A maximum of 125 vehicles have been allowed on the beach and the flats in years past — a limit often reached by 10 a.m. on weekends — and the four hours spanning low tide have become something of a paradise for beachgoers seeking a different experience at water’s edge.

Coolers are hauled far out on the flats, umbrellas raised, kayaks unloaded, grills put to use, and fishing poles stuck in the sand — far from the crowds and bustle often associated with Cape Cod beaches.

Under the new plan, 85 recreational vehicles would be allowed on the sandy beach above the high-water mark. That means fewer vehicles, on far less space.

But for Fitzgerald, who has multiple sclerosis, the ability to drive on the flats has helped him reach an area that might otherwise be inaccessible.

“My disease has made it harder for me to walk any distances, especially on the beaches. Crowes Pasture has allowed me to continue going to the beach in an enjoyable way and share that experience with my 6- and 9-year-old children,’’ Fitzgerald wrote to the commission.

Labdon said he understands that the Cape’s beaches need to be protected, but he is convinced the cars pose no danger to the flats.

“I know there are a lot of environmental folks with their heart in the right places who think this is damaging, but it’s not,’’ Labdon said. “There’s no sea life that you’re driving across, you’re not damaging the dunes, and to get there you’re driving 10 miles per hour through an established trail.’’

The board will take up the issue again on April 5, with a summer tradition hanging in the balance.

“Don’t ask me how this will end up,’’ Macdonald said, “because I don’t know.’’

Brian MacQuarrie can be reached at brian.macquarrie@globe.com.