The judge ruled officials short-circuited the open meetings and environmental laws before voting.

The lease is now void and Nassau County planning officials are left to start new hearings with the county legislature and vote again if they want to approve it.

The decision issued Thursday by Supreme Court Judge Sarika Kapoor is a big victory for Hofstra University, the plaintiff in the case whose campus is located next to the coliseum hub and opposes the casino plan.

Hofstra filed the lawsuit in April, claiming county planning officials and lawmakers failed to provide sufficient notice for public meetings and environmental review preceding votes in the spring.

“We appreciate the court’s thoughtful ruling and the court’s granting of reasonable attorneys’ fees and costs to Hofstra incurred in connection with several of the claims,” said Hofstra U. president Susan Poser.

“The court recognized the public’s right to participate in decision-making about the current redevelopment plan for the Nassau Hub. We look forward to contributing to the planning process and advocating for the use of the Hub in ways that will best contribute to our thriving community, while protecting against environmental and other harms,” the Hofstra honcho said.

The bombshell comes just days after Mets owner Steve Cohen unveiled his bid to erect a $8 billion casino-entertainment complex next to Citi Field as part of a rebranded Metropolitan Park.

Many of the heavyweight gaming operators are jockeying to win one of the three coveted state licenses to run a casino in the New York City metropolitan area, including Long Island and the northern suburbs.

“The respondents violated both the Open Meetings Law and SEQRA [State Environmental Quality Review Act] approving the lease transfer,” Kapoor, a 2004 Hofstra Law School graduate, said in her 32-page opinion.

Nassau County had no immediate official comment.

But Sands, in a statement, said it would not be deterred by the ruling.

“Las Vegas Sands is proceeding proudly and enthusiastically with our proposal for an integrated resort and entertainment center at the Nassau Hub.  We are grateful for the wonderful response we have received from the Long Island community and we will be continuing our very comprehensive outreach as we present this transformational project,” the company said.