A split ruling by New York’s top court could rebuild New York City’s real-estate taxation system—which litigants agreed is “disparate”—with one city attorney suggesting it might lead to an influx of owners protesting valuations.

The city’s decades-old system allows for caps to underassess condos and co-ops in affluent neighborhoods, while placing a heavier portion of the burden on neighborhoods of persons of color, to the tune of a $400-million-a-year disparity by some estimates.