A Canadian journalist working in Iran was arrested without charge on Sunday and has not been heard from since. Maziar Bahari, 42, a correspondent for Newsweek magazine, has been reporting on Iran for the past decade from his base in Tehran, where he was born. His most recent article for Newsweek, published in the aftermath of Iran’s disputed presidential election, examined opposition supporters’ concerns that groups loyal to President Mahmoud Ahmadinejad were staging violent incidents at their rallies to undermine support for their movement. “Newsweek strongly condemns this unwarranted detention, and calls upon the Iranian government to release him immediately,”...