Microsoft's plans to restrict third-party web browsers to Metro applications has drawn the attention of anti-trust officials in the US.
Mozilla and Google have both criticised Microsoft's plan to ensure that Internet Explorer is the only 'desktop mode' web browser on the ARM-powered Windows RT operating system.
The North American Senate Judiciary Committee plans to examine whether the allegations do indeed restrict the ability of Microsoft's browser rivals to compete on the new OS platform.
Both Mozilla and Google have complained that IE will have greater access to Win32 APIs than their own browser offerings which would make them uncompetitive in features and performance compared to Microsoft's own brand browser.
It's not really clear what the basis for such an antitrust motion is given that Apple is considerably more restrictive on the competing iOS platform. Safari is pretty much the only native browser that's allowed on Apple devices, with other browsers either reskinning the WebKit-based browser or using server side techniques to get around Apple's restrictions.
That said, Microsoft will need to tread carefully given the extensive history of antitrust investigations and unfavourable rulings and resulting settlements that have gone against the company in the US and in Europe.