A federal appeals court sharpened the pencil Tuesday on a 2010 U.S. Supreme Court ruling that requires evidence of a contractual basis in order for class arbitration to be enforceable.

That ruling “did not establish a bright-line rule that class arbitration is allowed only under an arbitration agreement that incants ‘class arbitration’ or otherwise expressly provides for aggregate procedures,” a three-judge panel of the U.S. Court of Appeals for the Third Circuit said in a precedential decision.