In the case of Lewis v. Clarke, the U.S. Supreme Court ruled that a tribal employee could not claim sovereign immunity for an off-reservation accident in his personal capacity. The case arose from a 2011 incident where William Clarke, a limousine driver employed by the Mohegan Tribal Gaming Authority, rear-ended Brian and Michelle Lewis on a Connecticut interstate highway while transporting patrons to the tribe's casino. The Lewises sued Clarke in state court for negligence but he claimed he was immune from suit due to tribal sovereignty as he was acting within his scope of employment during the accident. However, both lower courts rejected this argument and held him personally liable for damages caused outside reservation boundaries. The Supreme Court affirmed these decisions stating that although tribes have certain inherent powers of self-government including immunity from lawsuits, such protections do not extend to individual employees when they are being sued in their personal capacities even if they were performing duties related to their employment at time of incident.

In the dissenting opinion for Lewis v. Clarke, Justice Thomas argued that tribal sovereign immunity should extend to individual tribe members acting in their official capacity. He contended that the majority's decision was inconsistent with previous rulings and undermined tribal sovereignty by making a distinction between suits against individuals and suits against tribes themselves. According to him, when an employee is sued for actions taken within his or her scope of employment, it is essentially a suit against the employer - in this case, the tribe. Therefore, he believed that such lawsuits are barred by tribal sovereign immunity. Furthermore, he expressed concern about potential negative impacts on tribes' ability to govern themselves independently if they could be indirectly sued through their employees.