(a) An employee being laid off may displace another employee who has the least seniority points:
(1) in the same class or job series as the employee being laid off; or
(2) in any other class in which the laid-off employee previously held satisfactory nonprobationary status within the 36 months immediately prior to the effective date of the layoff.
(b) Subsection (a) of this section shall apply:
(1) first to the employee’s current appointing authority regardless of geographical area;
(2) if the provisions in paragraph (1) of this subsection are not available, to the employee’s current principal unit; or
(3) a secretary or head of a State principal unit may limit the displacement within the principal unit to one or more of the established geographical areas as prescribed by the Secretary.