Four weeks after winning a broad interpretation by the Supreme Court of one of the government’s main legal weapons in the “war on terrorism,” the Obama Administration has asked the Court to give officials wide-ranging legal immunity for enforcing another such law.  At issue in the just-appealed case of Ashcroft v. Al-Kidd (10-98) is a law that permits the arrest and detention of an individua sought as a “material witness” — a law that apparently has been used with some frequency in suspected terrorism cases.  The new petition, filed late Friday, is here; the lower court opinion is here.