A lawsuit filed by Kemper Freeman, Bellevue’s most prominent property owner, and eight other citizens over the voter-approved use of two center lanes of Interstate 90 for Sound Transit’s light rail project will be heard in front of the State Supreme Court in Olympia on Thursday.

The suit alleges that the Washington State Department of Transportation doesn’t have the right to let Sound Transit use the lanes for light rail because it was paid for using gas-tax funds, and therefore can only be used for highway purposes.

The lawsuit lists Gov. Christine Gregoire as the primary defendant in the case as well as Sound Transit and WSDOT.

Sound Transit argued in its response to the suit that the primary priority of the center lanes was not solely for automobile transit, and in 1976 all parties agreed to work toward a point where “conversion of all or part of the transit roadway to fixed guideway is possible,” according to Sound Transit’s response.

Voters approved the $18 billion extension of light rail out to the Eastside in 2008. Should the plan hold up as constituted, the center express lanes would close in 2015 for the beginning of construction work and reopen in 2021 as light rail lanes.