the last UN resolution lifts all sanctions: https://en.wikipedia.org/wiki/List_of_United_Nations_resolut...
> United Nations Security Council Resolution 2231 - Passed 20 July 2015. Endorsed the Iran Nuclear Deal and lifted all previous sanctions on Iran provided that Iran remains in compliance with its responsibilities in the nuclear deal.
(just went to wikipedia now, not an authority on the subject)
Since you already have the list, go back and click on each of the sanctions the UN passed before then.. and you'll see China voted in favor.
It's says so in the new report above. Also https://en.wikipedia.org/wiki/Sanctions_against_Iran although wikipedia, it clearly states UN had no banking restrictions over iran from 2006.
And of course the US has laws to enforce the sanctions they agreed (and China agreed) to implement under the UN resolutions.
It doesn't outlaw for example concrete just because concrete can be used to make nuclear reactors.
US sanctions, china never agreed on them. India another example didn't agree on them and traded oil with Iran for other non nuclear related items even during US sanctions. They didn't use US and EU banks to do this but they did indeed trade. The only problem here is Huawei used international banks to do the trade. The items are fine to be traded.