Five years after the “London Whale” trading scandal left JP Morgan Chase with losses of more than $6 billion, US regulators are having one last go at landing a catch. But only a minnow. The big fish, as usual, swim free.

The threat by the US Federal Reserve to take action against Bruno Iksil is another example of how unfair and ineffective regulators have been in their efforts to hold individuals to account for huge financial misdeeds. Whatever blame should attach to Iksil, his treatment looks like pretty rough justice. And however much he contributed to the losses, it seems wrong that the bigger fish, who were responsible for the lax controls that facilitated them, may escape the net. Frankly, it smells rotten.