Tamerlan Tsarnaev was apparently too dangerous to be allowed to go to Mecca, but not Boston. Saudi Arabia unofficially says that if Janet Napolitano read her mail, the Boston bombing might have been prevented. Britain's Daily Mail reported Tuesday that, according to a senior Saudi Arabian official, the Saudi government last year issued a written warning to our Department of Homeland Security about the danger of Tamerlan Tsarnaev, the dead lead suspect in last month's Boston Marathon bombings. Separate from Moscow's now-famous multiple warnings about Tsarnaev, the Saudi alert "was based on human intelligence developed independently in Yemen," according to...