This subchapter shall not restrict an employer's authority to prohibit the nonprescribed use of drugs or alcohol during work hours, or restrict an employer's authority to discipline, suspend, or dismiss an employee for being under the influence of drugs or alcohol during work hours, except as that authority is restricted under subsection 513(c)(3) of this title in reference to participation in an employee assistance program or suspension. (Added 1987, No. 61, § 1, eff. Sept. 1, 1987.)