Opposition to a new SoDo arena has one not-so-secret weapon that is unlikely to bring about any legal action.

Former Washington state Attorney General Rob McKenna told Seattle’s Morning News that city leaders can argue it’s in the public interest to keep Occidental Avenue South open. The city has said the road is key for both public and Port of Seattle traffic.

Mayor Ed Murray: Not pitting arena investors against one another

“Refusing to issue permits over competition would be arbitrary or capricious,” McKenna said. “Refusing to vacate a public right of way wouldn’t fall under the same standard. It’s more like a business decision for the city. They might be able to continue refusing to vacate Occidental and be OK legally.”

The city would have to vacate one block of Occidental Avenue South in order to build a new arena that would house NBA and NHL teams. The Seattle City Council voted against the street vacation 5-4 in May. The Port, like some city leaders, has said Occidental is crucial.

“Which I think is fiction,” McKenna said. “We’ve all been on it …”

The city is staring at the reality that if it steps aside and let investor Chris Hansen and his growing team — now with Seahawks quarterback Russell Wilson — build a basketball/hockey arena, it would be detrimental to the profitability of KeyArena. That’s the nature of competition, and the city can’t withhold approval of a new arena based on that alone, McKenna says.

Seattle Mayor Ed Murray said he is open to all options. That includes redeveloping the aging arena in Queen Anne.

“I would love to be the mayor that brings the Sonics back and brings hockey to this city,” Murray said. “How many cities would have five teams in their downtown core, if that happened? I think very few. Secondly, we need a different entertainment center. The current KeyArena is old and outdated, so either there or somewhere else in this county is going to be an entertainment arena and I would like that to happen in the core of the city.”

The mayor plans to issue a request for proposals in January for the possible redevelopment.

“We continue to listen to options to redevelop KeyArena as part of our revitalization of Seattle Center,” Murray said.