Donations to charity are tax deductible. But what if they are in the form of backdated stock gifts?

That seems to be the case in a new study from New York University finance professor David Yermack, reported in Porttfolio.com. Yermack's research was absolutely critical in the backdating revelations.

According to Yermack, chief executives and chairmen of public companies, including the likes of Sandy Weill, Barry Diller, and Stan O'Neal, had this extraordinary sixth sense when making charitable donations of stock to family foundations. They had this uncanny ability to make these gifts just before there was a decline in the stock price. Which meant they would get the maximum possible tax deduction.

If Yermack is right, it means these people just couldn't help ripping off the system. It was just well disguised as a gift to charity.

And of course, these sorts of gifts are exempt from insider trading rules. Which raises a number of questions. As Eleanor Bloxham, president of the corporate governance consultancy Value Alliance, told Portfolio.com: "Just because the form is different doesn't mean the substance of what these rules are about should be different. The same kinds of restrictions should apply to gifts as to regular insider trading."

She has a point. Still, creating restrictions around gifts becomes ridiculous and unwieldy. An alternative might be better rules around more disclosure when these gifts are handed out.