Apparently for the first time, state laws are being wielded against heavy Bitcoin traders. Florida prosecutors have charged three men, saying that their use of a site called localbitcoins.com violates laws against unlicensed money transmitters, according to a report in the Krebs on Security blog.

Krebs quotes UC Berkeley researcher Nicholas Weaver as saying he's unaware of any other case where state authorities took legal action against a Bitcoin vendor.

One user, named Michelhack, claimed to have transferred more than 150 bitcoins (around $110,000 in today's value) over the past six months. A law enforcement officer contacted Michelhack and said he wanted to use bitcoins to purchase stolen credit cards online. After one transaction, he set up a much larger deal, converting $30,000 in cash into bitcoins. Now prosecutors say Michelhack is 30-year-old Michell Abner Espinoza, of Miami Beach.

"[P]rosecutions like these could shut down one of the last remaining avenues for purchasing bitcoins anonymously," notes Krebs. He continues:

The court documents in this case also offer a great example of the traceability of Bitcoin transactions—a potential danger for both those seeking anonymous payments and for law enforcement officials posing as criminals as part of an undercover investigation... Weaver noted that, by examining the times and transactions in the criminal complaint, it appears that this is the Bitcoin wallet associated with the undercover officer.

The prosecutions come on the heels of the federal charges brought against the alleged CEO of BitInstant last month. That man, Charlie Shrem, was charged with plotting to sell $1 million worth of Bitcoin to use on the Silk Road drug-selling website.