City of Chicago laborers and streets and sanitation workers packed a Cook County courtroom Thursday to listen to more than two hours of legal debate about their retirement benefits. The scene mirrored the months of legal disputes over the funding of troubled Illinois state pension funds.

Stephen Patton, the City of Chicago’s top attorney, said the two city funds are likely to become insolvent, if not bankrupt, in the next dozen-or-so years if the judge rules against the city.

“What is the alternative?” Patton asked Circuit Court Judge Rita Novak.

Patton argued that if the judge strikes down city’s pension law approved by Illinois state lawmakers, then labor unions that oppose the pension changes will likely sue in a decade—when the pension funds will be so depleted, the accounts will have to pay-as-they-go as the bills come in.

But an attorney for the labor unions argues that changes to pension benefits are a violation of the state constitution’s language that says retirement funds can’t be diminished or impaired. Clint Krislov said the city’s argument that the funds will go insolvent in a decade equates to a Chicken Little ‘the-sky-is-falling’ defense; and said the retirement funds should’ve done more for the past several decades to force the city to put more into the accounts.

Earlier this year, the Illinois Supreme Court ruled in favor of the unions on a separate lawsuit involving reductions to state pension funds. That decision was heavily cited by the unions in their arguments. It’s also led to political leaders in Springfield to try and agree on a new legal strategy to change retirement benefits for state employees.

Tony Arnold covers Illinois politics for WBEZ. Follow him @tonyjarnold.