In a major blow to Gov. Chris Christie, a New Jersey judge ruled on Monday that he violated state law when he declined to make the full payment into the state’s pension system for public employees last year and ordered him to find a way to fund it now.

The decision further complicates Mr. Christie’s hopes of reviving his presidential ambitions, which have suffered in recent weeks as his approval ratings in New Jersey have sunk to the lowest point of his tenure, and Republican donors have moved to other contenders for the party’s nomination.

It came on the eve of his annual budget proposal to the Legislature, which already presented him with the challenge of finding $2.9 billion to make next year’s pension payment. The challenge is steep, with the state’s economy lagging well behind its neighbors’ and the nation’s, the state surplus dried up, and the governor loath to raise taxes.

Mr. Christie will now be scrambling also to find the $1.57 billion the judge ordered him to pay.

In an indication of the rebuke contained in her opinion, Judge Mary C. Jacobson of State Superior Court also ordered the administration to pay the legal fees of the several public sector unions that sued to force the payments.