An insider-trading case could be thrust back into court, with the Federal Police considering re-opening investigations of former Gunns timber boss John Gay.

Reports say police want to recover the money Gay made selling 3.4 million Gunns shares, just before the company's half yearly results were released and the share price dropped 20 cents.

Mr Gay pleaded guilty to the insider trading claims, which is extraordinarily rare for such a high-profile CEO. Still, he ended up $800,000 better off by selling shares when he did, courts heard in the trial. He was charged $50,000.

Professor David Chaikin from the University of Sydney Business School says police will have a hard time if they want to collect the money now, rather than at the time of the trial when it was frozen by court order.

“So if you haven't done that then you're really on the back foot and if you're talking about years ago and they haven't actually frozen that money then one would suspect that they've got major difficulties in doing that,” Prof Chaikin said.