The last remaining court challenge to the FCC's white space order was withdrawn Monday when the wireless microphone industry formally dismissed its petition for review of the regulations. 

The cancellation of the suit removes the last legal hurdle for the regulations, which allow devices to use vacant spectrum between television channels. 

The white space spectrum has been touted for a variety of uses, including rural broadband, machine-to-machine connectivity and so-called "Super Wi-Fi." The opening of the white space spectrum in 2010 marked the FCC’s first significant release of unlicensed spectrum in more than two decades.

The Alliance of Resident Theatres and a number of other groups including News Corporation, the National Basketball Association and the National Football League filed a Petition for Review in a District of Columbia Appeals Court in 2009.

The suit reflected concerns that FCC's 2008 white spaces order would create significant reliability issues with wireless microphones, which also use white space spectrum. 

Under a second set of FCC white space regulations put forth in 2010, locations where wireless microphones are used, such as theatres and stadiums, can be registered in the FCC's white space database, protecting them from interference from other devices using the unlicensed spectrum. 

It also set aside two channels for wireless microphones in 13 major markets. White space devices also must be able to "sense" wireless microphones as an added precaution against interference.

The dismissal of the suit comes one month after the National Association of Broadcasters dropped its petition for review of the 2008 white space order. The court had held both lawsuits in abeyance as the FCC reviewed petitions for its second report and order. 

The FCC issued an order addressing the petitions for reconsideration on April 5, resulting in the cancellation of the two remaining complaints against the white space regulations.