Conventional wisdom held that, once David Souter left the U.S. Supreme Court, he would retire to a life of relative seclusion back at his beloved, and decidedly rustic, Weare, N.H., family home.

Not so. Souter has moved to more modern digs in an upscale Concord, N.H., suburb and he’s moonlighting on the bench in Boston. In fact, lawyers appearing before the 1st U.S. Circuit Court of Appeals are routinely finding Souter on a panel, peppering them with the kind of penetrating questions that would send members of the Supreme Court bar searching for packets of Alka-Seltzer.