Judicial estoppel prevents a party from arguing two opposite positions
in separate proceedings. Is there a similar doctrine that applies to
argumentation in the same brief?
The general rule is that a party is permitted to argue inconsistent positions in the alternative within a brief. When a party does so without expressly saying so, it is assumed that they are arguing in the alternative unless the party clearly indicates otherwise (and is just being illogical).
But the law in the context of arbitration is a special case that doesn't align perfectly with the general rule, and makes different distinctions sometimes.
Under the substantive law of arbitration clause validity, sometimes a party can be forced to arbitrate even if there is a possibility that the underlying contract is unenforceable, with the arbitrator making that decision. But, a party cannot be forced to arbitrate in every case where the validity of the underlying alleged agreement is in doubt, simply because an agreement, on its face, contains or references an arbitration agreement.
Under the Federal Arbitration Act, certain preliminary decisions are vested in the courts even if a written arbitration purports to provide otherwise, if a party choses to raise those issues. A dispute over which of two significantly different competing arbitration agreements applies to an issue between the parties could be such a circumstance.
Thus, a term that provides that "delegates threshold questions such as the 'applicability, existence, scope, or validity' of the agreement to the arbitrator," is partially void as a matter of public policy under the Federal Arbitration Act, although some of its retains its validity.
For example, you can't delegate the question of the existence of an arbitration agreement to an arbitrator if that question is disputed, even if the contract says otherwise.
In arbitration cases, there is a rather elaborate jurisprudence governing what issues are for a court to decided and what are for an arbitrator to decision when the right of a party to arbitrate, and/or the validity of the underlying contract, are disputed, that makes some very fine distinctions between different kinds of arguments.
For example, if a party claims that he never had dealings with a party that presents an unsigned document that is a contract and also asserts that this party is bound to an arbitration agreement, that question can be decided by a court.
But, if a party signed an agreement with a plain vanilla arbitration clause but claims it is unenforceable because it was induced by duress or undue influence, the arbitration will usually go forward with the arbitrator deciding the validity of the contract.
When a decision is decided by a court, or by an arbitrator, is not easily summarized or manifestly obvious without a review of the relevant case law which is voluminous and intricate. See, e.g., Samson v. NAMA Holdings, LLC, 637 F.3d 915, 923 (9th Cir. 2011); Santich v. VGG Holding Corp., 2019 CO 67 ¶ 6 (June 24, 2019); N.A. Rugby Union, LLC v. U.S. of Am. Rugby Football Union 2019 CO 59, ¶¶ 20-22, 442 P.3d 859, 863-864 (June 17, 2019);;;