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.
Kayla Kelly-Slatten, UNCITRAL Transparency: An Examination of the 2014 Arbitration Transparency Rules and their Effect on Investor-State Environmental Disputes and Economic Fairness, 8 Y.B. Arb. & Mediation 94 (2016).