5 C.F.R. § 9701.402 – Coverage.

(a) This subpart applies to eligible DHS employees in the categories listed in paragraph (b) of this section, subject to a determination by the Secretary or designee under § 9701.102(b), except as provided in paragraph (c) of this section.
(b) The following employees are eligible for coverage under this subpart:
1. (1) Employees who would otherwise be covered by 5 U.S.C. chapter 43; and
2. (2) Employees who were excluded from chapter 43 by OPM under 5 CFR 430.202(d) prior to the date of coverage of this subpart, as determined under § 9701.102(b).
(c) This subpart does not apply to employees who are not expected to be employed longer than a minimum period (as defined in § 9701.404) during a single 12-month period.