UN had no banking restrictions on Iran if the activity was unrelated to nuclear proliferation. https://en.wikipedia.org/wiki/Sanctions_against_Iran

Additionally, the UN sanctions also prohibit banking services for prohibited items.

This is what Meng is accused of: attempting to transfer HP computers to Iran, and using the US financial system to do it. Both of these activities are prohibited by the UN sanctions.

Please reread the UN resolutions if you're unsure of this.

Edit: The bank fraud part is a US law, not under the UN sanctions.. But still that just means she committed bank fraud under US law in addition to breaking the sanctions.

https://www.international.gc.ca/controls-controles/about-a_p...

Which was used for its enforcement of the UN sanctions.

The list only includes very specialized computer hardware that can operate at very low temperatures or high radiation environments.

None of the news reports I've seen state that Huawei is being accused of violating UN sanctions. The US justice department sought Meng's extradition on the grounds that she committed fraud by lying to banks.

The violation of the sanctions would have been part of the extradition request if they were UN sanctions, as that would meet the dual-criminality bar, so given they're not, it's very likely these were US-specific sanctions, and the extradition request was made on the grounds of the fraud charge because, unlike the sanctions violations, it could potentially meet the requirement of dual-criminality.