Embarrassed by a prostitution scandal, the Secret Service will assign chaperones on some trips to enforce new rules of conduct that make clear that excessive drinking, entertaining foreigners in their hotel rooms and cavorting in disreputable establishments are no longer tolerated. The stricter measures, issued by the Secret Service on Friday for agents and employees, apply even when traveling personnel are off duty. The policies, outlined in a memorandum obtained by The Associated Press, are the agency's latest attempt to respond to the scandal that surfaced as President Barack Obama was headed to a Latin American summit in Cartagena, Colombia,...