What defines a sub-agent's authority in the context of delegation?

In the context of delegation, a sub-agent's authority is defined primarily by the express authority granted by the principal to the agent. For a sub-agent to have authority to act on behalf of the principal, the principal must authorize the agent to delegate that authority to the sub-agent. This express authority is crucial because it establishes the boundaries within which the sub-agent can operate, ensuring that the principal retains control over who acts on their behalf and the scope of that action.

While it might seem that an agent could freely appoint anyone or that authority could be implied or automatic, such assumptions do not account for the critical role that the principal's instruction plays in the delegation process. The principal's express consent is necessary to maintain the integrity of the agency relationship and protect both the principal's interests and the obligations placed on the agent and sub-agent. Therefore, the requirement of express authority reflects the legal principles governing agency relationships and the necessity for clear communication regarding authority limits.