Beijing just put the EU on notice. China's commerce ministry sent a 30-page warning to Brussels.
The message is simple. If the EU forces Huawei or ZTE out of 5G networks, China will hit back at EU firms.
The wording inside is sharper than the polite tone Europe usually gets.
The EU law would do something the bloc has only ever asked for before. It would force member states to rip out gear from any firm tagged a security risk.
The law would set a three-year window to do it. It would also let the EU label a whole country a "cyber threat."
Firms from that country could then be locked out of telecom networks first. A long list of other industries would follow.
That list takes in connected cars, power grids, water systems, cloud computing, medical devices, space services, and chips.
In short, the law treats network gear the way airport security treats luggage. A country lands on the no-fly list. None of its hardware gets through.
The trade office's note did not hint. China spelled out the threat in plain terms.
If the EU starts pulling Chinese gear out of networks, "China can launch relevant investigations into the EU or EU businesses, and take reciprocal measures."
Beijing also said the law "violates multiple WTO rules." It warned that "economic cooperation will be inevitably pushed towards de facto decoupling" if it passes.
China asked for the entire "countries posing cybersecurity concerns" section to be cut from the draft.
That is not a quiet note. That is a setup for a court fight.
EU firms in China are stuck. They are caught between two legal systems that disagree, and per the EU Chamber of Commerce in China, their members would struggle to comply with laws at home and in China at the same time.
That is real risk for EU stocks with deep ties to China.
Chinese firms feel the same heat on the other side. Last week, scanner maker Nuctech sued the EU. The case covers older subsidy rules.
China's supply-chain rules give Beijing more tools too. Those tools include exit bans, travel bans, and bans on deals.
The trigger phrase: "investigating Chinese supply chains." That is a lot of leverage. It targets EU bosses who travel to China for work.
This fight is part of a longer trend. The EU and China have been trading blows for two years.
The fights cover chips, EVs, and now cyber gear. Each side has built new legal tools to use against the other.
Each side keeps testing those tools. The cyber law would be the biggest test yet.
It would also lock the EU into a path that is hard to walk back. EU firms with big China sales are watching closely.
So are Chinese telecom giants who still depend on the EU market.
The EU's cyber law was first announced in January. It is still in draft form. Beijing wants the toughest sections cut entirely.
Brussels has not signaled it will back down. The next round of EU-China trade fights starts when this draft moves to a formal vote.