In 2003, Thomas Carbonneau wrote that "freedom of contract . . . Is at the very core of how the law regulates arbitration," and he referred to this as "Contract's Empire." I think Carbonneau is right and that, if anything, arbitration law has moved even further since then in the direction of contract.
Nicolette Chasse, Success at Mediation: How to Define and Accomplish It, 8 Y.B. Arb. & Mediation 297 (2016).