Montgomery County’s efforts to keep a 16-pump gas station from coming to Wheaton are not legal, the county attorney’s office said.

ZTA 12-07, proposed in April by Councilman Marc B. Elrich (D-At large) of Takoma Park, would ban any gas stations with more than 3.6 million gallons of annual volume from being built within 1,000 feet of any school, park, playground or other cultural, entertainment or recreational use.

The proposed change “is not a proper exercise of the District Council’s authority,” according to an opinion from Clifford Royalty, the county’s chief of the Division of Zoning, Land Use and Economic Development. The opinion was sent to County Executive Isiah Leggett (D) on July 18 via County Attorney Marc Hansen.

Drawing on case law, the opinion concluded the zoning change violated the 14th Amendment to the U.S. Constitution as well as Article 24 of the Maryland Declaration of Rights and would not be upheld if reviewed in court.

When a statute is challenged under Maryland Article 24 and the 14th amendment, a court considers whether the law, as an exercise of a state’s police power, has direct relation to public health, morals, safety or welfare, the county opinion said.

County health officials were unable to determine if large gas stations posed a credible health risk.

If enacted, the ZTA would be arbitrary, and it would constitute illegal spot zoning because the change only would apply to a station at the Costco under construction in Wheaton, according to the opinion.

The Costco station at Westfield Wheaton shopping mall would be the county’s largest, with an expected annual volume of 12 million gallons per year. It would be within 1,000 feet of the Kenmont Swim & Tennis Club near University Boulevard.

“It is apparently undisputed that the ZTA would apply only to the Costco station and that it would prohibit the station,” the county’s legal opinion offered. “It also appears, to the detriment of the ZTA, that the ZTA was intended to prohibit the Costco station and cause its pending application for special exception to be denied.”

In a response written to the county council Friday, the Kensington Heights Civic Association argued that in a prior ZTA requested by Leggett, the council considered a zoning change that would allow automobile filling stations “by right” in commercial zones, “when located in a regional shopping center.”

In 2010, the council opposed that change.

“The County Executive’s goal was to allow Costco to sidestep the Special Exception process and go straight to building permit — and the only property in the county that would have benefited from the proposed amendment was the Westfield Wheaton Mall Property,” the association wrote. “ZTA 12-07 does not constitute ‘spot zoning’ under any theory.”

The civic association has led a two-year fight against the station.

Calling the opinion an “eleventh-hour submission” that purports to analyze the pending change only to find it unlawful, the citizen association said it was writing to express its extreme disappointment.

“Not only is the legal analysis of County Attorney Marc Hansen, deeply flawed, but the timing of this submission to the County Council is suspect,” the association wrote.

Senior Legislative Attorney Michael Faden said previously that county attorney opinions are taken under advisement by the council and council staff when making decisions, but are not binding.

The council’s Planning Housing and Economic Development Committee, chaired by Councilwoman Nancy Floreen (D-At large) of Garrett Park on July 9 voted 2-1 to not recommend council approval of the zoning change after county health officials could not determine if mega gas stations posed a health risk. Elrich, who sits on the committee, voted in favor of his legislation.

The council is scheduled to vote on the ZTA Tuesday during its district council session, tentatively planned for 1:45 p.m.