45 USC 797b - Preferential hiring

(a) General 
Any employee who is deprived of employment shall have the first right of hire by any other railroad for a vacancy for which he is qualified in a class or craft (or in the case of a non-agreement employee, for a non-agreement vacancy) in which such employee was employed by the Corporation or a predecessor carrier for not less than one year, except where such a vacancy is covered by
(1)  an affirmative action plan, or a hiring plan designed to eliminate discrimination, that is required by Federal or State statute, regulation, or Executive order, or by the order of a Federal court or agency, or
(2)  a permissible voluntary affirmative action plan. For purposes of this section, a railroad shall not be considered to be hiring new employees when it recalls any of its own furloughed employees.
(b) Status 
The first right of hire afforded to employees under this section shall be coequal to the first right of hire afforded under sections 907 and 1004 of this title.