MARBELLA, Spain—On a rainy winter evening, an inflatable police boat approached an imposing 60-foot, four-engine vessel suspected of ferrying drug smugglers. Rather than try to flee, the larger speedboat began circling the inflatable, taunting the four Civil Guard officers aboard. Onshore, an audience cheered the drug boat. Olé! Olé, they yelled, as if spectators at a bullfight. Bro, kill them.   The drug boat then smashed into the Civil Guard vessel, flying over the top and crushing the crew. It circled back and struck the officers who had been knocked overboard. Two were killed. The high-profile attack showcased the reach,…