Huawei is suing the United States over policies banning the use of the company’s equipment by the government. It’s the latest escalation in a continuing battle over Huawei’s position in the US.

The suit alleges that policies passed by Congress last year as part of a defense spending package unconstitutionally singled out Huawei for punishment. When Congress passed the legislation, it included provisions blocking Chinese-made telecommunications equipment from being used in federal networks, effectively also preventing major government contractors from using Huawei equipment. The measure specifically named Huawei and ZTE, as well as some other Chinese companies.

The company says that the measure breached a legal standard against making a “bill of attainder,” in which the government makes policy punitively directed at a small group. The suit also accuses the government of infringing on the company’s due process rights.

Accuses the US of passing a “bill of attainder”

Huawei executives announced the suit during a press conference in Shenzen. The company’s rotating chairman Guo Ping said in a statement at the conference that, after failing to mollify the concerns of US lawmakers, “we are left with no choice but to challenge the law in court.” As they have in the past, Huawei executives argued at the press conference that a ban on Huawei is not only unnecessary, but that America will be left behind in the buildout of next-generation 5G networks.

US officials have repeatedly branded Huawei as a potential security threat, arguing that the company could be used by the Chinese government as a tool for spying. Huawei has consistently denied that possibility, saying that the US has failed to produce evidence of its concerns. The measures preventing government equipment use have been one of the clearest actions against the company in the US.

In recent years, Kaspersky Lab, a cybersecurity company based in Russia, was also roiled by allegations of potential espionage. The company filed a suit similar to Huawei’s, but has not been successful. Huawei, which is asking a court to rule that the US’s current policy is unconstitutional, will likely need to differentiate itself from that case.

The largest provider of telecommunications equipment in the world, Huawei has faced scrutiny from lawmakers and intelligence officials over its operations, seemingly without end. As it battles policy measures, the US is also seeking the extradition from Canada of the company’s chief financial officer, who has been accused of violating sanctions against Iran. The company, which has denied wrongdoing, has also been charged in the US with stealing trade secrets from T-Mobile. The Trump administration, meanwhile, has reportedly been considering an order that would further restrict the sale of Huawei’s products, and the US has been pressing allied countries to drop the company’s equipment.