(Newser) – Mitt Romney's tax returns—and the bevy of offshore tax havens they point to—have already provided lots of fodder for critics, but all generally agree that he's done nothing illegal. "But it is worth asking if it is actually true," writes Nicholas Shaxson in Vanity Fair. "The answer, in fact, isn't straightforward." Shaxson investigated Romney's financial records, and while he didn't find any concrete evidence of wrongdoing, he says Romney "seems comfortable striding into some fuzzy gray zones." For example:

Romney's "blind trusts"—designed to keep politicians away from their money so they won't have conflicts of interest—don't look very blind. His personal lawyer runs one, which just happened to invest $10 million in a startup co-founded by his eldest son and a longtime campaign fundraiser.

Mitt has an IRA account with $102 million in assets—even though, over the 15 years he contributed to it, he should only have been able to contribute $30,000 a year. One possible explanation: He might have loaded it with staggeringly undervalued stock in Bain companies, which could then grow tax-free.

Romney's hedge fund investments are a complete mystery, because he claims the funds won't tell him about the underlying assets. Coincidentally, many were set up in the Cayman Islands, where divulging such info is illegal.

The Romneys continue to earn millions in carried interest from Bain for "performing services," which critics say is a "perversion of the law," given that Romney left Bain a decade ago.

There's also a Bermuda-based company wholly owned by Romney himself that he neglected to mention in several financial disclosures and tax returns. Its value is a mystery, too, so "it is possible Romney's wealth is even greater than previous estimates."

For the full article, click here , and for more on his financial disclosures, click here . (Read more Mitt Romney stories.)