In the 1941 case of Parker, Deputy Commissioner, United States Employees' Compensation Commission v. Motor Boat Sales Inc., the U.S. Supreme Court ruled in favor of Parker and upheld a compensation claim made by an employee who was injured while working on a boat that was docked and under construction. The court determined that although the vessel was not yet launched or completed, it still constituted as a "vessel" under federal law because it was intended to be used for navigation upon water once finished. Therefore, employees working on such vessels are entitled to receive compensation for injuries sustained during their work according to maritime laws and regulations. This ruling clarified legal definitions within maritime law regarding what constitutes a "vessel", expanding protections for workers involved in shipbuilding activities.

In the dissenting opinion for Parker v. Motor Boat Sales, Inc., it was argued that the majority's decision to deny compensation to an employee injured while performing work-related duties on a vessel not owned by his employer contradicted previous rulings and interpretations of the Longshoremen's and Harbor Workers' Compensation Act. The dissenting justices believed that this act should be interpreted broadly in order to provide protection for workers engaged in maritime employment, regardless of whether their injury occurred on their employer’s property or another’s. They contended that denying coverage based solely on where an accident took place would lead to arbitrary results and undermine the purpose of worker protection laws. Furthermore, they disagreed with the majority's interpretation of "employer" as only referring to owners or operators of vessels, arguing instead that any person who employs others in maritime service is considered an employer under this law.