Recently, American unions have pushed hard to increase their power in the employment market. Unions may strike and thereby shut down a reluctant firm to extract a favorable deal, and will often do so even though that strike action imposes economic losses on union members. But just how hard will unions press to get a strongly pro-union labor contract? Last week in Glacier Northwest v. International Brotherhood of Teamsters, the US Supreme Court heard oral argument on a case that will help answer that question.

In Glacier, the union and the employer were locked in protracted negotiations over a new contract. The company uses cement mixers to distribute its ready-mix product to its customers. Just as the contract was about to expire, union drivers, as part of a coordinated effort, took their loaded trucks on the road, only to return the trucks, still loaded, to the company headquarters moments after the contract expired. The drivers left the engines running to prevent the immediate hardening of their cargo. However, owing to the large number of nearly simultaneous truck returns, much of that cargo did harden, inflicting immediate property damage on the trucks. The two sides reached agreement on a new contract a week later, but the dispute over these losses lingered on. The parties disagree over whether the actions of these workers came within the protected strike practices under the National Labor Relations Act (NLRA). Employers must bear losses caused by strike practices that the NLRA protects, but employers may sue unions in state court in tort for deliberate physical injuries.

This distinction makes a substantial difference. State courts hear and decide cases far faster than the National Labor Relations Board does. More important, state courts can award substantial monetary damages against unions while the NLRB cannot. Given these institutional differences, the key cat-and-mouse game is whether the case goes first to the state court or to the NLRB. The traditional practice on sequencing the two proceedings was set out in the important 1959 labor case, San Diego Building Trades Council v. Garmon, which held that the plaintiff may bring a tort action right away, to which the defendant might plead that the case was “arguably” subject to the provisions of the NLRB as a defense. Upon the defendant pleading such a defense, the tort suit had to be discontinued. The Supreme Court in Garmon ruled that the NLRA required a state court to dismiss a tort suit alleging that a union wrongfully attempted to win a contract by picketing an employer’s place of business. Indeed, that lawsuit was blocked even though the NLRB declined jurisdiction over the case, and even though the state court wanted only to award damages rather than impose an injunction against the union. The coercive effect of damages could induce abandoning the very behavior that the injunction would have directly prohibited. The question in Glacier was whether this employer was caught by Garmon pre-emption.