The ruling, which was announced on Monday, comes as a significant and unexpected setback for Mr. Emanuel, who has been a front-runner both in polls and in fund-raising in the race to replace Richard M. Daley, the city’s longest-serving mayor, who will retire this spring.
The question of Mr. Emanuel’s residency — and whether he had lived in Chicago long enough to appear on the city’s ballot — had been a matter of debate since Mr. Emanuel departed the White House last fall to run for mayor.
Mr. Emanuel contended that he had always maintained a home in Chicago, the city where he was born, and that his time at the White House was a matter of national service. But Mr. Emanuel’s opponents said he did not meet the state’s residency requirements to run for a mayoralty, one of which is to have lived in the city for a year before the day of the election. His return to Chicago in the fall, they argued, was too late to qualify for a Feb. 22 ballot.
The Chicago Board of Elections concurred with Mr. Emanuel, as had a Cook County trial judge. But a three-judge panel of the Illinois Appellate Court ruled against him, 2 to 1. With time running short and ballot arrangements already being finalized, the issue seemed certain to go to the State Supreme Court.