Page "Unfair labor practice" Paragraph 18

Not every unfair act amounts to an unfair labor practice ; as an example, failing to pay an individual worker overtime pay for hours worked in excess of forty hours in a week might be a violation of the Fair Labor Standards Act, but it is unlikely to amount to an unfair labor practice as well.

Similarly, a violation of a collective bargaining agreement, standing alone, may not constitute an unfair labor practice unless the employer has not only violated the contract but repudiated all or part of it.