The European Commission has taken the extraordinary step of threatening to sue the United Kingdom if President Trump exempts Britain from U.S. tariffs on steel and aluminium.

The U.S. President has suggested that the tariffs — designed to protect the American aluminium and steelworkers from foreign dumping, as their industry is a strategic asset — will not be applied to all of America’s allies, with NAFTA members Canada and Mexico already being offered exemptions.

But the European Commission — the unelected body with acts as the EU’s executive as well as the sole initiator of EU-level legislation — has reacted with fury to British trade secretary Liam Fox suggesting that the United Kingdom will try to “maximise the UK’s case” for a similar exemption and threatened to sue the country if it does not suffer along with the rest of the bloc, the Telegraph reports.

Brussels Prepares to Drag Britain into ‘Trade War’ with America https://t.co/r3Ny0pA5ax — Breitbart London (@BreitbartLondon) March 2, 2018

“The UK has to respect the rules,” declared a senior official. “I don’t think there’s any question that if Mr Fox was going to decide to negotiate on this issue, he would be acting against the rule of law, against the rules of the EU.”

Jyrki Katainen, one of the European Commission’s vice-presidents, added: “We expect the whole EU to be treated as a trading bloc … We cannot accept that the EU is divided into different categories. All our member-states are bound to the same set of rules when it comes to trade.”

While it is true that EU member-states are not allowed to strike their own trade deals (one of the key arguments for leaving the bloc, according to Brexit campaigners) it is not clear that there were any rules requiring Britain to subject itself to the same third-country tariffs as other EU members, even if those third countries did not insist on applying them to Britain — until now.

President Trump Gets Tough on EU After Juncker Threatens Taxes on Jeans, Bourbon, and Harley-Davidsons https://t.co/Lis71DLBx3 — Breitbart London (@BreitbartLondon) March 3, 2018

The United States is an important export market for Britain’s small steel industry, accounting for over 15 per cent of exports — although it is not any real threat to American workers, making up only a very small percentage of total imports.

For Germany, the EU’s dominant member-state and number eight in America’s top ten sources of steel imports, it is a different story — which might explain the EU’s hostile line.

Follow Jack Montgomery on Twitter: @JackBMontgomery