MANILA, Philippines — The federal agents were waiting at the Philippine Senate to serve an arrest warrant. Their target was a lawmaker. But the lawmaker ran, and the agents gave chase. He dashed up flights of stairs and through doors, stumbling at one point. A couple of minutes later, he was in the safety of the Senate chamber, where the would-be arresting officers had no authority. This extraordinary scene was captured on closed-circuit television and shown during a plenary session of the Senate on Monday. The senator in question was Ronald dela Rosa, who was the chief enforcer in former President Rodrigo Duterte’s devastating antidrug campaign. He is wanted by the International Criminal Court in The Hague for crimes against humanity, the same charge that it arrested Duterte for last year. For now, dela Rosa, 64 — whose nickname is “Bato,” or rock in Tagalog — is holed up in the Senate. “I am well rested and have already recovered from the adrenaline rush yesterday,” he said in a text message Tuesday.…