Okla. Stat. tit. 60, § 175.716

CERTAIN DISTRIBUTIONS PROHIBITED A. Except as provided by subsection B of this section, an authorized trustee shall not exercise a power to distribute principal of a trust otherwise provided by Section 3 or 4 of this act if the distribution is expressly prohibited by the terms of the governing instrument of the trust. B. A general prohibition of the amendment or revocation of a trust or a provision that constitutes a spendthrift clause shall not preclude the exercise of a power to distribute principal of a trust under Section 3 or 4 of this act.