When can an agent legally delegate contractual duties to a sub-agent?

The correct answer is that an agent can legally delegate contractual duties to a sub-agent in accordance with trade custom and necessity. This means that if the practices in a particular industry or market commonly support the delegation of certain tasks to sub-agents, an agent may do so without needing explicit permission each time from the principal. This delegation is often guided by the standards of practice that are recognized and accepted within that trade.

The concept of necessity also plays a pivotal role in allowing delegation, where situations arise that require the agent to act promptly, and a sub-agent is a practical solution to fulfill the obligations contained within the contract. This typical understanding helps maintain the efficiency and effectiveness of business operations.

In contrast, the need for explicit permission by the principal is not a requirement in cases where customs support delegation; hence, the option about needing explicit permission is less applicable. The idea that an agent can delegate when the primary contract is vague misinterprets the nature of delegation, which relies more heavily on established customs rather than ambiguity in contractual terms. Finally, the notion that an agent can delegate "whenever they see fit" overlooks the importance of customary practices and the necessity of fulfilling a principal's expectations and obligations.