I guess there is still remaining trade volume that could be further reduced by sanctions. While it is a tenth of what is typically traded with other countries in the region, I would say it is still 1000 times higher than the trade with North Korea. Having said that, the example shows that cruel dictators can still survive in isolation (particularly if the rest of the world still continues to be split on basic human rights)

> European governments could expel Iranian ambassadors as a start

why should they, those ambassadors represent millions of Iranians who showed in support of their country on Monday, Jan 12

"More than 36,500 Iranians were killed by security forces during the January 8-9 crackdown on nationwide protests, making it the deadliest two-day protest massacre in history,"

Too bad that this is also a first time in history, following massacre of protesters: https://en.wikipedia.org/wiki/Trial_and_execution_of_Nicolae...