It is challenging for a layperson to decipher the cryptic zoning codes that govern the city’s buildable space, and it is even harder to imagine that minute changes to those regulations made in a small room in Lower Manhattan can have a real, quantifiable effect, miles away.

Yesterday, when the city’s Department of Planning unanimously approved a downzoning of a distant Queens community, Bayswater, which sits on the boarder of Nassau County, a property owner said the decision stripped away a significant amount from the value of their property – $400,000 to be exact.

The new, more restrictive zoning laws – which are nearly certain to receive approval from the City Council in the next 60 days – would limit the property owners from receiving what they see as the full value of their property. The family of Judge Pauline Newman, a federal Court of Appeals judge appointed by President Reagan, and her grandniece, Natalie Prokoff, a lawyer for the city, has owned the lot in question for decades.

Their 3,000-square-foot house, decaying but still stately, overlooks Jamaica Bay and has distant views of the Manhattan skyline. Judge Newman and Ms. Prokoff put the house on the market and had offers in the range of $500,000 to $600,000. They were told that if they sold it to a developer instead, they could get about $1.4 million. They entered a contract with a developer who planned to build six new houses on the lot. When the developer heard about the proposed downzoning in January, the contract was revoked.

The property owners went to a Planning meeting last month to argue that the new zoning plan should be redrawn with the new boundary excluding their lot. Commissioners considered their proposal in a subsequent review session, but they decided to leave it in.

Now the owners say they are considering legal action against the city or the area’s civic groups, which had aggressively sought both the downzoning proposal and the inclusion of their particular property.

Judge Newman compared the city’s actions to using eminent domain and likened it to seizures that are enabled by last year’s U.S. Supreme Court ruling in Kelo v. New London, which allows a city to invoke eminent domain for the sake of private economic development.

Yesterday’s decision was applauded by many Bayswater residents, who believe their neighborhood’s unique character is under assault and that increased density puts pressure on the area’s infrastructure, including its roads, schools, parking, and sewer system.

A Bayswater resident who testified before the Planning Commission in favor of the downzoning, Eugene Falik, said Judge Newman and Ms. Prokoff’s loss was necessary for the greater good. “That is the price that society extracts for a civilized system,” he said. “They would make more money if they could build a 50-story apartment building there. Should we allow that?”

“The point of zoning is to place limits on how much money people can extract from every inch of land for the overall benefit of the community and the city,” Mr. Falik said. “The zoning should not make it worthless. But it doesn’t need to make it as valuable as it can be.”

In the Department of Planning’s review session about Judge Newman and Ms. Prokoff’s property, the chairwoman, Amanda Burden, said that six houses on the site would be “too tight,” and she noted “very, very strong” community support for including the property, which is on the most scenic strip of Bayswater.

“It’s appropriate because it will still allow the property owner to develop,” Ms. Burden said of the new regulations at a hearing earlier this month. She said it still allows for “non-hardship development.”

The downzoning of Bayswater is just one example of nearly 50 lower density or contextual rezonings undertaken by the Department of Planning during the Bloomberg administration, many of them in far-flung communities in Queens, Brooklyn, the Bronx, and Staten Island.

A vice president for research at the Regional Plan Association, Christopher Jones, acknowledged the increasing conflict between property owners who want to extract a profit from their homes and neighbors who want to preserve their communities. He said it is a result of the development pressure on the city’s residential communities from rising population projects and a changing suburban landscape in counties outside city limits.

“The places people used to go when they wanted a suburban lifestyle no longer have the growth in the housing market or the low-cost housing to allow people to come in who want to move out of Manhattan or an apartment in Brooklyn,” Mr. Jones said. “That is putting a lot of pressure on neighborhoods like Bayswater.”

“What they are going through is very similar to what Nassau and Westchester and Bergen counties have already gone through – a lot of community opposition to further development and additional density,” Mr. Jones said.

“Whenever you do a rezoning of any type, the odds are that somebody’s property values drop, and other peoples’ increase,” Mr. Jones said. “Where you draw the line, that’s a tough thing.”

Judge Newman believes she happens to be on the wrong side of that line.

“If we spend several hundred thousand in legal fees, we might have a modest shot at beating this thing,” she said yesterday, adding that the community singled out her property for inclusion.

“We are thinking that we could make an argument that this is not what zoning is about,” she said. “They are irrationally trying to preserve a quaint Victorian cottage that they aren’t even willing to buy at a very reduced price.”

Ms. Prokoff said, “Whatever benefit the community gets for two less houses on this property, it does not weigh the economic detriment it costs us.”