A federal judge in Chicago recently certified a class of over 1,700 members and beneficiaries against CITGO Petroleum Corp., after rejecting the fuel company’s summary judgment motion in a suit alleging it underpaid pension plans by upwards of $31 million.

U.S. District Judge Matthew F. Kennelly’s ruling will allow the plaintiffs’ case to move forward to trial against the gas and energy giant, alleging it violated the federal Employee Retirement Income Security Act by it imposing a “marriage penalty” on pension plans’ joint and survivor annuity recipients.