By now, we all know (and if you don’t, it might be time to start looking at those advance sheets again): Data searches of cellphones incident to arrest run afoul of the Fourth Amendment. As late as February, however, what now seems obvious was a real legal conundrum. In fact, in People v. Cregan — a case I wrote about in the March 24 edition of the Daily Law Bulletin (“Bag search case could catch SCOTUS’ eye”) — the Supreme Court held that “personal items such as cigarette …