The US International Trade Commission has ruled against InterDigital in a complaint that alleged Huawei, Nokia, ZTE had infringed the company's patents.
On Thursday, the ITC upheld a previous ruling in June that found Huawei, Nokia and ZTE had not infringed on the seven InterDigital patents named in the complaint.
Filed in 2011, the InterDigital case had sought an import ban by the U.S. on older 3G phones from the three handset makers.
InterDigital said it was disappointed with the ITC decision, and would appeal it. It has another petition pending with the ITC that is targeting 3G and 4G products from Huawei, Nokia, ZTE and Samsung.
The complaint, filed in January, accuses the four companies of infringing up to seven of its cellular-related patents. InterDigital asked for an import ban into the U.S. on Samsung's Galaxy S III, the Nokia Lumia 920, and other smartphones from the handset makers, which the ITC is authorized to impose in some cases of patent infringement.
InterDigital is a US-based research company that develops wireless standards and holds 20,000 patents. The company, however, has drawn criticism for being a "patent troll," a claim InterDigital rejects, pointing to its 200 engineers that work on new technologies.
Not all are convinced. The Chinese government in September launched an anti-monopoly investigation against InterDigital, which the company said was the result of its patent lawsuits targeting Huawei.
InterDigital now alleges that China is threatening to arrest its employees. This week, the company was scheduled to dispatch staff to the country for talks with China's National Development and Reform Commission. But on Friday, the government body said it could not guarantee the safety of employees sent to the country, according to InterDigital spokesman Patrick Van de Wille.
"There are not a lot of ways to perceive this positively," he said on Tuesday. "Even if the NDRC does back track and guarantees their safety, we don't even know if we would believe them."
The NDRC could not be reached for comment. US chip maker Qualcomm is also facing an anti-monopoly probe from the Chinese regulator.