This article does not apply:

1. (1) To any employee or employer covered by the federal Railway Labor Act, 45 U. S. C. §151, et seq.;
2. (2) To any employee of the United States or a wholly owned corporation of the United States;
3. (3) To any employee who is employed on property over which the United States government has exclusive jurisdiction for purposes of labor relations; or
4. (4) Where the provisions of this article would otherwise conflict with, or be preempted by, federal law.