Hoffman Plastic Compounds v NLRB, the Supreme Court held 5 to 4 that an undocumented worker could not claim back pay, after being discharged for organizing in a union. The gradual withdrawal of more and more people from the scope of labor law, by a slim majority of the Supreme Court since 1976, means that the US falls below international law standards, and standards in other democratic countries, on core labor rights, including freedom of association. Common law tests were often important for determining who was, not just an employee, but the relevant employers who had "vicarious liability". Potentially there can be multiple, joint-employers could who share responsibility, although responsibility in tort law can exist regardless of an employment relationship. In Ruiz v Shell Oil Co, the Fifth Circuit held that it was relevant which employer had more control, whose work was being performed, whether there were agreements in place, who provided tools, had a right to discharge the employee, or had the obligation to pay. In Local 217, Hotel & Restaurant Employees Union v MHM Inc the question arose under the Worker Adjustment and Retraining Notification Act of 1988 whether a subsidiary or parent corporation was responsible to notify employees that the hotel would close. The Second Circuit held the subsidiary was the employer, although the trial court had found the parent responsible while noting the subsidiary would be the employer under the NLRA. Under the Fair Labor Standards Act of 1938, 29 USC §203(r), any "enterprise" that is under common control will count as the employing entity. Other statutes do not explicitly adopt this approach, although the NLRB has found an enterprise to be an employer if it has "substantially identical management, business purpose, operation, equipment, customers and supervision." In South Prairie Construction Co v Local No 627, the Supreme Court found that the DC Circuit had legitimately identified two corporations as a single employer given that they had a "very substantial qualitative degree of centralized control of labor", but that further determination of the relevant bargaining unit should have been remitted to the NLRB. When employees are hired through an agency, it is likely that the end-employer will be considered responsible for statutory rights in most cases, although the agency may be regarded as a joint employer. Contracts of employment When people start work, there will almost always be a contract of employment that governs the relationship