The ruling was the latest installment in the long-running Linux intellectual property rights legal case between IBM and SCO.
The feud started in spring 2003 when SCO claimed its code had been used by IBM to develop commercial Linux products.
Roger Bickerstaff, a partner in IT law at Bird & Bird, said if SCO found any disputed code, it could renew its claim for licence fees from Linux suppliers and users.
Bickerstaff said if SCO was successful in claiming parts of its code had been used in Linux, there would be the question of how intrinsic it was to Linux.
The open source community could take the code out of the operating system or build an alternative system, he said.
IBM denies any infringement to SCO's intellectual property. Next month Novell, which supplies SuSE Linux, will face SCO in the courts. SCO has already lost an appeal on its efforts to sue car firm DaimlerChrysler over its Linux use.