Markus Ferber, a senior member of the European Parliament, says regulators in Europe and the U.S. have only recently realized inherent danger in a footnote to rules on swap-execution facilities. Any platform that allows more than one participant to trade swaps with two or more participants must register as an SEF, according to the footnote, which is scheduled to go into effect Wednesday. Market experts are warning about unintended consequences. "People may fall back to trade on a bilateral basis," ISDA CEO Robert Pickel said. "That's one of the options still available."