Malcolm Gladwell's "semi-defense" for Enron in New Yorker

Malcolm Gladwell's article in the current issue of the The New Yorker is a self-described "semi-defense." From his blog:

200701031020
Can anyone explain -— in plain language -— what it is Jeff Skilling and Co. did wrong?

I'm not asking for an explanation for what they did wrong as businessmen. That's plain. They did a mountain of stupid and arrogant things. Nor is this about what Skilling and company did that was unethical or in bad faith. There's a mountain of evidence on that too. The question is strictly a legal one: according to the way the accounting rules were written at the time, what specific transgressions were Skilling guilty of that merited twenty-four years in prison? For the sake of argument, let's stipulate that summaries must be three sentences or less.

Link