within the Department of Homeland Security (or a predecessor agency or subdivision transferred into the Department) is within a unit that is not appropriate for representation by a labor organization under such chapter, are null and void, except to the extent that such determinations were made in accordance with the criteria outlined in paragraph (1), (2), (3), (4), or (7) of section 7112(b) of such title 5. (c) Clerical amendment The table of chapters for part III of title 5, United States Code, is amended by striking the item relating to chapter 97. 638. Establishment of specialized inspector occupations The Secretary of Homeland Security shall establish within the Bureau of Customs and Border Protection 3 distinct inspectional occupations: immigration, customs, and agriculture. These divisions shall coordinate closely with each other under the direction of a high-level official within the Bureau, but shall report to separate operational chains of command. 639. Increase in inspectors at airport and land border inspection stations In each of the fiscal years 2017 through 2021, the Secretary of Homeland Security shall increase by not less than 1,000 the number of positions for full-time active duty immigration inspectors at airport and land border inspection stations within the Department of Homeland Security above the number of such positions for which funds were allotted for the preceding fiscal year. 640. Law enforcement retirement coverage for inspection officers and other employees (a) Amendments (1) Federal Employees Retirement System (A) Paragraph (17) of section 8401 of title 5, United States Code, is amended by striking and at the end of subparagraph (C), and by adding at the end the following: (E) an employee (not otherwise covered by this paragraph)— (i) the duties of whose position include the investigation or apprehension of individuals suspected or convicted of offenses against the criminal laws of the United States