 The Erie Doctrine, adopted in 1938, held that while Federal law was determinative in procedural matters, state law should control for substantive matters, thus preventing 'forum shopping' between state and Federal courts.The defendant in "Guaranty Trust" argued that the plaintiff's action was time-barred under a New York statute of limitations.The plaintiff countered that the relevant statute of limitations was "procedural," was not "substantive" law, and therefore was not within the ambit of the doctrine established in the Erie case.