; and (ii) any individual entitled to a survivor annuity (based on the service of an incumbent, or of an individual under clause (i), who dies before making an election under paragraph (3)(B)), to the extent of any rights that would then be available to the decedent (if still living). (8) Rule of construction Nothing in this subsection shall be considered to apply in the case of a reemployed annuitant. 641. Reestablishment of the United States Border Patrol anti-smuggling unit The Secretary of Homeland Security shall reestablish the Anti-Smuggling Unit within the Office of United States Border Patrol, and shall immediately staff such office with a minimum of 500 criminal investigators selected from within the ranks of the United States Border Patrol. Staffing levels shall be adjusted upward periodically in accordance with workload requirements. 642. Establishment of specialized criminal investigator occupations The Secretary of Homeland Security shall establish specialized Criminal Investigator occupations within the Department: one for the investigation of violations of immigration laws, another for customs laws, and a third for agriculture laws. These divisions shall coordinate closely with each other under the direction of a high-level official within the Department, but shall report to separate operational chains of command. 643. Establishment of career paths to criminal investigator positions The Secretary of Homeland Security shall ensure that all persons selected for criminal investigator positions within the Department of Homeland Security possess a minimum of 3 years of field experience within the Department or its predecessor agencies in the specialized area of law that will be investigated. 644. Additional immigration enforcement agents In each of fiscal years 2017 through 2021, the Secretary of Homeland Security shall increase by not less than 500 the number of positions for full-time active duty immigration enforcement agents responsible for transporting and guarding detained aliens above the number