A fight is brewing between a Wall Street utility and a federal regulator over who will control potentially lucrative trade data in the $639 trillion swaps market.

At issue is the destination of derivatives-trading data generated to comply with new transparency rules. The Commodity Futures Trading Commission proposed several months ago that traders should comply with the new requirements using data repositories of their choosing, but in November changed tack after its proposals were challenged in a lawsuit filed by one such provider, a unit of CME Group.