Okla. Stat. tit. 6, § 6-1733: Written agreements or instruments - Designation of law

governing.

Any trust institution that maintains a trust office or

representative trust office in this state and its affected clients

may designate this state, a state where affected clients reside, or

the state where such trust institution has its principal office, as

the state whose laws shall govern any written agreement between such

trust institution and its client or any instrument under which the

trust institution acts for a client.