The playing field for U.S. legal tender and virtual currencies has just been levelled a bit.

The U.S. Treasury, through its Financial Crimes Enforcement Network, has issued guidance clarifying that while users of virtual currencies (such as bitcoin and Amazon Coins) are not considered money services businesses, virtual currency exchanges and administrators are MSBs and are subject to U.S. government regulations.

According to a report by Finextra, this means that firms such as CoinLab which bitcoin has retained to handle its North American operations of its currency exchange service, Mt.Gox, must meet MSB regulations.

This could be a costly proposition for such companies, which must obtain MSB licenses in every state where they intend to provide services. Bitcoin magazine said this would require "tens of thousands of capital to acquire in each state.

Read the entire U.S. Department of the Treasury FinCEN guidance document.

Read more about regulatory issues.