The Wisconsin Employment Relations Commission sought to hold a union liable for an unfair labor practice, by refusing to work overtime.

An employer claimed to the National Labor Relations Board that his staff had committed an unfair practice by refusing to work overtime, but this was dismissed, as there was no violation.

Justice Brennan held that the Wisconsin Supreme Court had not been entitled to make a ruling against the union, because its jurisdiction was preempted by the National Labor Relations Act.

This line of pre-emption analysis was developed in San Diego Unions v. Garmon, supra, and its history was recently summarized in Amalgamated Association of Street, Electric Railway & Motor Coach Employees v. Lockridge, 403 U.S. 274, 290-291, 91 S.Ct.

Thus, for example, some early cases suggested the true distinction lay between judicial application of general common law, which was permissible, as opposed to state rules specifically designed to regulate labor relations, which were pre-empted.

Others made pre-emption turn on whether the States purported to apply a remedy not provided for by the federal scheme, e. g., Weber v. Anheuser-Busch, Inc., 34U.S.

It was, in short, experience not pure logic which initially taught that each of these methods sacrificed important federal interests in a uniform law of labor relations centrally administered by an expert agency without yielding anything in return by way of predictability or ease of judicial application.

However, a second line of pre-emption analysis has been developed in cases focusing upon the crucial inquiry whether Congress intended that the conduct involved be unregulated because left "to be controlled by the free play of economic forces."

This Court did not inquire whether Congress meant that such methods should be reserved to the union "to be controlled by the free play of economic forces."

Rather, because these methods were "neither made a right under federal law nor a violation if it" the Court held that there "was no basis for denying to Wisconsin the power, in governing her internal affairs, to regulate" such conduct.