Clifton McClelland, the attorney for Sens. Arthenia Joyner and Thad Altman, argued that the Florida Rail Act passed by the Legislature in December 2009 and approved by then-Gov. Charlie Crist obligates Scott to allow construction of the line.
He noted that the Legislature appropriated $130 million in federal money to get the project started.
The judges, though, hammered McClelland with questions about whether that appropriation would extend to the full $2.4 billion award, which would cover nearly all of the construction rail line's construction costs.
"The project cannot go forward without further appropriations by the Legislature. Isn't that correct?" asked Chief Justice Charles Canady. "This is a project that is still very much in expectancy. It's not something the Legislature has fully authorized."
Gov. Rick Scott's attorney, Charles Trippe, argued that ruling in favor of Altman and Joyner and pressing for construction of the rail line would involve also requiring the Legislature to appropriate additional money, forbidding Scott from vetoing the appropriation.
"The scope of this is vast," he said.
Earlier Thursday, the mayors of Tampa, Lakeland and Orlando said Thursday that they have received assurances from the U.S. Department of Transportation that Florida would not have to pay back $2.4 billion if the high-speed rail project failed.
"If there is one point that I would like to get across to every single Floridian who is concerned about this issue, it is this: There is absolutely no risk to the Florida taxpayer in moving forward with the high-speed rail project," Tampa Mayor Pam Iorio said. "If the governor continues to maintain that there is risk to Florida taxpayers, it is inaccurate."