Is Bitcoin a currency? People use it to buy things. Is it a security? Securities are traded on Bitcoin-denominated exchanges. Is it a commodity? “We are looking into that,” Mark Wetjen, acting chairman of the Commodity Futures Trading Commission said earlier this month.

Fed chair Janet Yellen has said the Fed has no jurisdiction over Bitcoin but called on Congress to investigate. In January, Treasury Secretary Jacob Lew said  the U.S. needed more time to assess the ”phenomenon” of Bitcoin to ensure it isn’t used for illegal purposes.

Created in 2009, Bitcoin is a popular virtual currency traded anonymously online without banks acting as middlemen. It isn’t tied to any country or controlled by a central bank, but it can be cashed in for dollars and other official currencies. It came to popular attention with the collapse Mt. Gox, the largest Bitcoin exchange, and several others in February, and Newsweek’s controversial “outing” of the currency’s anonymous creator, Satoshi Nakamoto — a claim called into question by the media frenzy that ensued.

Nobody is regulating Bitcoin. But everyone is investigating it. Most recently, it’s the Securities and Exchange Commission.

On March 3, they sent a letter to Mircea Popescu asking about the sale SatoshiDice, an online Bitcoin gambling business, on MPEx, the Bitcoin-based online exchange run by Popescu.

Specifically, the agency wanted the account statements of SatoshiDice founder Erik Vorhees, and any contracts or documents related to the listing or sale of shares in his company.

Popescu confirmed receipt of the letter to Bloomberg News and denied violation of any laws. A spokesman for the SEC would not confirm or deny the inquiry, Bloomberg said.

The Bitcoin entrepreneur sold his online gambling business last year for $11.5 million worth of bitcoins, in what was the first major Bitcoin acquisition, according to Venture Beat. It’s the sort of thing regulators like to keep an eye on, but the SEC hasn’t figured out whether they can even regulate Bitcoin exchanges.

That hasn’t stopped them from asking questions though.

Popescu was ready for them. He posted a copy of the SEC’s request on his website along with an email back-and-forth between himself and SEC lawyer Daphna Waxman.

Popescu responded mockingly, disputing at length the legality of the SEC’s request.

After giving her a verbal spanking, he did leave room for future cooperation:

“In the spirit of candor, let me make it perfectly clear that what’s being discussed here is nothing else and nothing short of the SEC’s ultimate relevancy and importance in the Bitcoin space, and so far I am not particularly impressed. Let us work together to improve upon this shaky basis if at all possible.”

But then he said he wanted a bunch of impossible (at least in the near term) stuff before the two could talk frankly, including an SEC determination that it lacks jurisdiction over Bitcoin.

Popescu dismissed the idea that the SEC has authority over MPEx and other Bitcoin exchanges on his website. Others in the bitcoin community are less cavalier about the potential for regulation. “….Negative pressure from the SEC could have a huge chilling effect,” the Bitcoin journal BitcoinX said.

Some are on board with regulation of the virtual currency, the highest profile among them being the Winklevoss twins (Tyler and Cameron), who have already registered their Bitcoin business with the SEC.