If the individual named in the trust instrument accepts the office of trustee, he or she will have an affirmative duty to act pursuant to the terms of the trust. Missouri law provides that upon acceptance of a trusteeship, the trustee shall administer the trust in good faith, in accordance with its terms and purposes and the interests of the beneficiaries and in accordance with Sections 456.101 to 456.11-1106 RSMO.

The Uniform Trust Code comments to this section provide in part that a primary duty of a trustee is to follow the terms and purposes of the trust and do so in good faith. Additionally, Section 456.8-801 RSMO provides that the trustee must administer the trust in accordance with the terms and purposes of the trust, but the trustee must also comply with Missouri State law as set forth in the MUTC statutes.

While the trustee must follow the purposes and terms set forth in the trust instrument, a trustee is not required to follow a provision in the trust that the trustee knows would be unlawful or invalid because the provision would be contrary to public policy. Missouri law provides in part a trust may be created only to the extent its purposes are lawful, not contrary to public policy and possible to achieve.