In the Armour & Co. v. Wantock et al., 1944 case, the U.S Supreme Court ruled in favor of employees who were required to be on-call at their employer's premises during non-working hours. The plaintiffs, firemen employed by Armour & Co., argued that they should receive compensation for this time as it was spent predominantly for the company’s benefit rather than their own leisure or personal activities. The court agreed with them and held that under Fair Labor Standards Act (FLSA), such time is considered working time and therefore must be compensated accordingly even if no actual work is performed during these periods. This ruling set a precedent for future cases involving similar issues about compensable work hours.

In the dissenting opinion for Armour & Co. v. Wantock et al., Justice Frank Murphy argued that the majority's decision to allow compensation for time spent on-call was a departure from established principles of wage and hour law, which traditionally only compensated workers for actual work performed. He contended that this ruling could lead to an unreasonable expansion of compensable time, potentially including any period where an employee is subject to call, regardless of whether they are actually working or not. This would place undue burden on employers and disrupt the balance between employer and employee rights in labor relations. Furthermore, he disagreed with the majority's interpretation of "work" under Fair Labor Standards Act (FLSA), asserting it should be strictly defined as physical or mental exertion controlled or required by employer and pursued necessarily primarily for benefit of employer’s business.