It seems that Cisco’s (CSCO) efforts to hit back at patent trolls have hit a potentially fatal roadblock. Although the networking equipment vendor last year decided to go on offense against firms that buy patents in bulk and sue other companies for infringement despite not making any products of their own, the Wall Street Journal reports that a federal court has shot down one of Cisco’s first major attempts to go after an alleged patent troll. According to the Journal, U.S. District Judge James F. Holderman this week “that the aggressive licensing strategy used by [patent holding firm] Innovatio IP Ventures LLC against Cisco customers is protected by the U.S. Constitution.”

Cisco last year filed a complaint against the Chicago-based Innovatio for allegedly using “misleading, fraudulent and unlawful” tactics in their attempts to extract patent royalties, including allegedly sending threatening letters to Cisco’s customers and “allegedly paying witnesses for testimony and documents in order ‘to overcome fatal shortcomings’ in patent-infringement claims.” At the time, Cisco general counsel Mark Chandler accused firms such as Innovatio of engaging in “shakedowns” of legitimate companies and vowed to “make them liable for racketeering.”