In the case of Eagar et al. v. Magma Copper Co., 1967, the plaintiffs were a group of taxpayers who filed suit against Magma Copper Company for allegedly avoiding paying its fair share of taxes by undervaluing its property in Arizona. The Supreme Court ruled that federal courts should abstain from deciding on state tax matters unless there is no plain, speedy and efficient remedy available at the state level or if there are extraordinary circumstances where necessary to prevent immediate irreparable injury. In this case, it was determined that an adequate remedy existed within Arizona's legal system for resolving such disputes over property valuation and taxation issues; therefore, federal court intervention was not warranted.

In the dissenting opinion for EAGAR et al. v. MAGMA COPPER CO., it was argued that the majority's decision failed to consider important aspects of labor law and policy, particularly in relation to collective bargaining agreements. The dissent criticized the majority for not taking into account whether or not a grievance procedure existed within such an agreement, which could have been used by employees to address their concerns about wage deductions before resorting to litigation. Furthermore, they contended that allowing individual lawsuits over minor contractual disputes undermined union representation and disrupted industrial peace by encouraging fragmented litigation instead of collective action through unions. They also pointed out inconsistencies in how federal courts had previously interpreted similar cases involving state laws regulating employment contracts and suggested this inconsistency created confusion rather than clarity in labor law jurisprudence.