A court ruling in Loudoun County apparently has cleared the way for development there of a major shopping center, another in a ring of regional malls that increasingly determine shopping, employment and social patterns in Washington's suburbs.

Windmill Center, a 1.1 million-square-foot development proposed by the Lerner Corp. at the intersection of Rtes. 7 and 28 would become the commercial focus for Loudoun County and Herndon in Fairfax County, planners said. It also would draw shoppers from Reston to the east and from as far away as Winchester to the West while generating more than $50 million in annual sales, according to the developers.

The Circuit Court ruling went against the County Board of Supervisors, which opposed the development partly on grounds that Loudoun is not ready for it, lacking sufficient police, fire and sewer services. The board probably will decide next week whether to appeal the case, according to Board Chairman George Yeager.

Windmill Center would be the latest in a string of Lerner developments that include the Tysons Corner, White Flint, Landover Mall and Wheaton Plaze shopping centers.Other major centers are open or in planning stages in Manassas, Dale City, Springfield, Fairfax City, Rockville, Laurel and southern Prince George's County.

The regional centers have moved farther and farther out from the older communities inside the Beltway, often springing up near lower cost housing developments in the outer suburbs that previously had only the barest shopping facilities.

Containing a multitude of department stores, specialty shops, restaurant and theaters, these regional centers can provide a day of shopping, dining and entertainment for people who have been used to driving great distances or shopping at scattered sites.

At the same time they can severely damage business at shops and stores in the old "downtown" areas of cities, older suburbs and small towns and are often flanked by strip development.

Tysons Corner, probably the most spectacularly successful of the centers, has turned a once rural cross-roads into an employment center for 14,000 people and one of the hottest real estate properties in the nation.

It is Tysons Corner's success that has made Windmill Center feasible, according to John T. Hazel Jr., attorney for the Lerner-Route 7 Limited Partnership in its suit against the county.

Hazel said, "Tysons is saturated, with not enough outlets to fill the demand. Current demand for regional center facilities in Northern Virginia far exceeds the supply."

Hazel said there would be at least 100,000 people and perhaps as many as 150,000 in the primary trade area of the center when it opens in 1981 or 1982.

The developers estimated that the center would result in gross sales of about $93 million in 1984, generating sales taxes of $1.8 million and property tax of $576,000 for the county.

Lerner had sought to have 177 acres of a 420 acre tract rezoned from industrial to commercial use but was turned down by the county supervisors on Dec. 16, 1975.

The county's comprehensive plan had called for a shopping center at the Rte. 28-Rte. 7 intersection and the county's planning staff had recommended approval of the rezoning.

However, after what local officials recall as an overwhelmingly hostile reaction from the largest turnout at a public hearing in the county's history, the supervisors rejected the rezoning problems and emotional lives of his [TEXT OMITTED FROM SOURCE].

William C. Crossman Jr., then the board chairman, said yesterday that he opposed the plan because "I thought the county wasn't ready. We have no paid fire department and no paid police department. It was putting the cart before the horse. I don't think anybody voted the way they did because of the pressure but it was clear that the people testifying didn't want it."

Supervisor Frank Raflo said, "I considered its costs effectiveness to the county to be negative. The impact on small towns, landfill, sewer capacity were weighed against the real estate and sales tax and I found it lacking at that time."

Loudoun County Circuit Court Judge Rayner Snead has now ruled that the board's rezoning denial "was clearly unreasonable, arbitrary and capricious" in light of the staff approval, the master plan and the board's failure to ask for changes in the rezoning application of any further studies Snead also found that the action was "confiscatory" since there was no other reasonable use for the land.

Hazel said the developers would "await the county reaction on appeal and then decide what to do next."

Hazel said he hoped that all planning could be completed in time for ground breaking next year and an opening in 1981.

Hazel said the center has no commitments from stores at this time but would like representatives from "the typical dozen from Sears to Bloomingdales."

The development would include a Rte. 7 overpass so no left turns would be required to enter the mall and its associated office building and industrial park sites.

The loss of this zoning case, the recent loss in a nearby residential zoning case and several recent rezonings in the Rte. 7 corridor insure that the area will continue the development that has shifted the balance of population to the eastern edge of Loudoun County.

The county also is involved in at least four other rezoning suits with the total number of housing units involved topping 10,000 - a potential growth of 30,000 people in a county with a present population of about 57,000.

"I don't know if the stopper has been let out of the bottle or not," said Crossman of the board's slow growth - critics called it "no growth" - policies. "If the money markets open up we could see another building boom."