U.S. President Donald Trump has followed through with his threat: Since June 2018, steel and aluminum imports from the EU are subject to tariffs, justified with national security considerations. Such a breach of WTO law should not be tolerated. The EU’s rebalancing measures are thus an important political signal. At the same time, tit-for-tat retaliation will harm everyone. If Trump wants to strengthen the industrial base in the United States, he should rather invest in education and infrastructure.