This rule, effective June 1, 2009, finalizes the second phase of a joint Department of Homeland Security and Department of State plan, known as the Western Hemisphere Travel Initiative (WHTI), to implement new documentation requirements for U.S. citizens and certain nonimmigrant aliens entering the United States. The final rule details the documents U.S. citizens and nonimmigrant citizens of Canada, Bermuda, and Mexico are required to present when entering the United States from within the Western Hemisphere at sea and land ports-of-entry.