the closing is of a temporary facility or the closing or layoff is the result of the completion of a particular project or undertaking, and the affected employees were hired with the understanding that their employment was limited to the duration of the facility or the project or undertaking; or

the closing or layoff constitutes a strike or constitutes a lockout not intended to evade the requirements of this chapter. Nothing in this chapter shall require an employer to serve written notice pursuant to section 2102(a) of this title when permanently replacing a person who is deemed to be an economic striker under the National Labor Relations Act [29 U.S.C. 151 et seq.]: Provided, That nothing in this chapter shall be deemed to validate or invalidate any judicial or administrative ruling relating to the hiring of permanent replacements for economic strikers under the National Labor Relations Act.