Purpose Loses: Federal Subject Matter Jurisdiction to Compel Arbitration Limited by Congressional Use of "Arising Under" to well-pleaded complaint

Not a surprise, but a brief and unanimous case that might have escaped you:  court holds that power to compel arbitration in federal court is limited to well-plead claims.  The party who wanted to rely on a counterclaim to support jurisdiction tried arguing policy and purpose, but the court relied on Congressional use of "arising under" to require the well-pleaded complaint rule apply.  the case, Vaden v. Discover Bank, is here.