In all the media coverage surrounding the Saudi Arabian-led bombing campaign in Yemen in recent days, few have stopped to ask a fundamental question: Is it legal? Yemen’s President Abdu Rabu Mansour Hadi had specifically called for an intervention as rebels from the Houthi movement threatened his rule. But having overstayed his term in office, resigned once and even fled the country, Hadi’s legitimacy as ruler is shaky, legal experts say, placing the Saudi military action in murky legal territory. “If Hadi were still in Sana’a and had a relatively modest rebel...