Ever since George Washington included arbitration provisions in his will, this idea has kicked around.  Washington’s will contained this language:

"That all disputes (if unhappily they should arise) shall be decided by three impartial and intelligent men, known for their probity and good understanding; two to be chose by the disputants each having the choice of one, and the third by those two – which three men thus chosen shall, unfettered by law or legal construction, declare their sense of the Testator’s intention; and such decision is, to all intents and purposes, to be as binding as if it had been given in the Supreme Court of the United States."

John T. Brooks and Jena L. Levan writing for Wealth Management reviewed the state of the law in December 2013. See their article here.

On March 11, 2014 a California appellate court refused to enforce a mandatory arbitration provision. In the case of McArthur v. McArthur, No. A137133 (Cal.App. 1 Dist. Mar. 11, 2014)

Outsourcing Justice comments on the McArthur case as follows:

"The California appellate court also refused to enforce the arbitration provision and affirmed the denial of the motion to compel. The appellate court acknowledged the Texas and Arizona decisions involving arbitration clauses in trust agreements, as well as a few other decisions involving the trust fact pattern, and the appellate court reasoned that the plaintiff sister in this case was not attempting to accept benefits under the amended trust or enforce rights under the amended trust. Instead, the plaintiff sister argued the amended trust is invalid and should be set aside. As a result, the appellate court reasoned the plaintiff sister had not consented to the terms of the amended trust, and hence the plaintiff sister was not bound to arbitrate."