The top land-use attorney for the Montgomery County government said Wednesday that the a bill that would block plans for a gas station at the Costco under construction next to the Wheaton Mall is unconstitutional.

The opinion, issued by Associate County Attorney Clifford L. Royalty, is likely to stir further debate on the bill, which was introduced by County Council member Marc Elrich (D-At Large) in April in response to community health concerns about the gas station.

The bill prohibits large gas stations from being built within 1,000 feet of schools or recreational facilities. Costco’s proposed gas station would be within 1,000 feet of a swimming pool.

The County Council is expected to vote on the bill on Tuesday. County Executive Isiah Leggett (D) opposes the legislation.

In the opinion, which Leggett requested, Royalty and Hansen said the bill improperly singles out Costco and does not further “a legitimate governmental objective.”

“You have requested our opinion as to whether [the bill] is legal,” they said. “We have concluded it is not.”

In response, Elrich said council lawyers disagree with that opinion and plan to publicize their concerns at council meeting on Tuesday. He added that the opinion represents the executive branch’s attempt to block the bill and that Royalty and Hansen are ignoring the real purpose of the bill — to protect public health.

“If that’s their best defense, it’s pathetic,” he said.