It seems like a classic case of closing the barn door after the horses have gotten out.

The Landmarks Preservation Commission voted on Tuesday to declare a row of 26 19th-century town houses and tenements on the north side of Tompkins Square Park in the East Village a historic district. But there was just one problem: A building project that the designation was intended to prevent received a permit from a different New York City agency just hours before and now, essentially, cannot be stopped.

Preservationists had pressed the commission to move quickly to designate the north side of East 10th Street between Avenues A and B a historic district. The street has what the commission itself said is “an unusually intact row of single family row houses, including some dating to the 1840s, mid-to-late 19th Century tenements and the circa 1904 Tompkins Square branch of the New York Public Library, already a city landmark.”...