That is because your are looking in the wrong place. Please refer to the Joint Comprehensive Plan of Action. In the JCPOA sanctions are regulated.

As long as Iran agrees to nuclear restrictions in exchange for the financial benefits of sanctions relief (as agreed in the JCPOA), the other members should be safe from a legal standpoint.

Additionally, the EU Blocking Statute [1] came into force, mitigating any sanctions that the US might impose due to companies trading with Iran.

[1] http://europa.eu/rapid/press-release_IP-18-4805_en.htm

Certainly sanctioned or fined European banks would have the ability to challenge the measures in a US court.

On the other hand, sanctions on a state are usually met with an equivalent response, and the only question is how powerful the other side is. In the case of the EU, the answer is, not powerless.

Look, the US has a lot of cards to play. But randomly bullying banks who didnt do anything wrong, as per your suggestion, is not a particularly effective one, so they won't do that.

You said it: non-arbitrary

All completely legal tho

How ironic that you do not even realise how entitled you are to make such a remark. The EU is regulating its own markets. The US is trying to stop the EU from trading with Iran.

Think about what you're saying. If you read British history, the empire before this one, we used military dominance to force China to allow our companies to deal opium to their society, totally ravaging it. You're makinga similar argument except instead of opium it's surveillance capitalism. Whether or not you think SC is bad, it's hard to justify why countries shouldn't be allowed to take their own approach to what's allowed through their borders. And why countries should allow companies with natural monopolies and mayb massive profit margins to basically milk their citizens. Honestly I wish the EU /really/ did tech protectionism.