Okla. Stat. tit. 60, § 60-175.9
Trustee lending funds to self, affiliate, etc
Except as provided in Section 10, no corporate trustee shall
lend trust funds to itself or an affiliate, or to any director,
officer, or employee of itself or of an affiliate; nor shall any
noncorporate trustee lend trust funds to himself, or to his
relative, employer, employee, partner, or other business associate.