Texas Property Code - PROP § 112.051. Revocation, Modification, or Amendment by Settlor

(a) A settlor may revoke the trust unless it is irrevocable by the express terms of the instrument creating it or of an instrument modifying it.

(b) The settlor may modify or amend a trust that is revocable, but the settlor may not enlarge the duties of the trustee without the trustee's express consent.

(c) If the trust was created by a written instrument, a revocation, modification, or amendment of the trust must be in writing.