A more thorough explanation:

The No Further Inquiry Rule is a legal principle that applies to situations where a trustee engages in self-dealing. This means that the trustee is using their position to benefit themselves instead of acting in the best interests of the beneficiaries they are supposed to be serving. Under this rule, any transactions that the trustee enters into for their own benefit are automatically considered voidable by the beneficiaries, without the need for further proof that the transactions were harmful or unreasonable.

For example, let's say that a trustee of a trust decides to sell a piece of property that is owned by the trust to themselves at a price that is below market value. This would be considered self-dealing, as the trustee is using their position to benefit themselves at the expense of the beneficiaries. Under the No Further Inquiry Rule, the beneficiaries would be able to challenge this transaction and have it voided without having to prove that it was harmful or unreasonable.

Another example of self-dealing that would be subject to the No Further Inquiry Rule would be if a trustee used trust funds to invest in a business that they owned or had a stake in. Again, this would be considered a breach of the trustee's fiduciary duty to act in the best interests of the beneficiaries, and the beneficiaries would be able to challenge the transaction without having to provide further evidence of harm or unreasonableness.