Whether dedicated bus lanes along Post Oak violate Metro’s 2003 commitment to build light rail is beyond the determination of the Texas Attorney General’s Office, the state's top attorney decided.

The opinion, eagerly awaited by critics and supporters of the bus project, appears to give Metropolitan Transit Authority a path to partnering with the Uptown Houston Management District and associated tax increment reinvestment zone for lanes between a Bellaire Transit Center near U.S. 59 and Northwest Transit Center near Interstate 10.

In the ruling, Attorney General Ken Paxton said the issue centered on the $640 million in bonds voters approved.

“A court would likely determine that (Metro’s) contract with the voters included the expenditure of a portion of the bond proceeds on the Uptown/West Loop 4.4 mile rail segment,” Paxton wrote. “Whether Metro's participation in the Uptown Houston Transit Project violates that contract with the voters requires the resolution of fact issues that are beyond the purview of an attorney general opinion.”

Metro officials, as part of a litany of arguments submitted that Paxton did not find as important, said the bond money was used for the Green Line and Purple Line light rail routes that opened in May, and a Red Line extension that opened in December 2013.

A court ultimately, if asked, would have to decide whether voters in 2003 received the benefits Metro promised them, and that money was used for those purposes, the opinion said. Another question, Paxton said, would be whether the existing project “will prevent the development of the promised rail segment.”

That could be a key distinction. Metro, to secure Texas Department of Transportation approval for planned bus lanes along Loop 610, indicated the bus project was not a precursor to rail. While that could make developing rail along the same route more difficult, as curves and overpasses might have to be redesigned, it does not technically prevent a light rail from ever happening.