Bear in mind that most of the time, sanctions not only prevent you from doing business with the sanctioned entity, but also with any other entity that's doing business with them.
Can you point to any notable instances of such arguments?
(It's easily searchable I'm sure, but I'd appreciate any tips you have).
But the whole bureaucratic issues are not to be underestimated. At some point, the US eased the sanctions on Iran a bit (under Obama I think), and my former colleague tells me that quite a few European companies were up for doing business with Iran (related to your regular old passenger cars in that case). At some point the sanctions got reinstated, and several German and French companies were threatened with sanctions if not outright sanctioned. My former employer (before my time there) had 2 projects worth ~$5M (of 2010s US dollars, not the monopoly money I earn now) total with some of these companies, and both were axed, even though the company itself had absolutely nothing to do with Iran. They got some compensation, but like not even 10%. Apparently, the whole sanctions thing is considered a "special case" in contracts.