When the U.S. Supreme Court scolded the Bush Administration last year for attempting to try suspected enemy combatants on the cheap, the ruling rested largely on one of the court's most honored precedents. It's the same opinion that helped force Richard Nixon to cough up those embarrassing tapes in 1974. And for more than 50 years it has guided the court in deciding whether a President has acted within his powers or whether he has stepped over the line.
The interesting thing is, it's not a majority opinion. It's a concurrence, a separate statement that a lone Justice, Robert Jackson, cooked...