Gary Gensler spent much of the past month fending off Wall Street's campaign to slow the move to electronic swaps trading. So when the platforms went live last week, the top U.S. derivatives regulator wasn't going to let a government shutdown stop him from monitoring its progress.

With most of the staff at the Commodity Futures Trading Commission's Washington headquarters on furlough, Gensler, in his final months on the job, had to pick up the phone and call around to make sure the system was working. He pronounced himself satisfied.

“It was a very good start,” he said in an interview. “Though the CFTC is in darkness with the shutdown, we've been able to bring some additional light to the marketplace.”