A trade embargo does nothing if any middleman can funnel goods and money across by simply misrepresenting or omitting details about where the goods are going.
If I’m wholesaling Cisco routers and they show up in Syria or Iran, and Cisco and I can prove we didn’t know how they got there , that still doesn’t make it okay.
You can still be held responsible. The law requires you to check on who the final customer is and to take some actions on any suspicious transaction. Someone will come knocking on your door and you will need to show documentation to support your assertion that you "couldn't have known". If a product is subject to a trade embargo you can't just "sell it to a middleman" and turn a blind eye.
Wasn't really aimed at either. But maybe to answer the question: if Huawei acts as a middleman that buys embargoed goods from the US and then sells them to a country under embargo then under US laws both Huawei and whoever sells to Huawei can be held responsible (individuals and the company as a whole), the place the actions take place aren't relevant as far as I know. Even companies selling their own product to embargoed countries without any US involvement face economic sanctions under US laws (though their executives presumably would not be arrested.)
If HP (A US company) sells to a middleman without knowing who the final customer is for embargoed goods then HP and its executives can be held legally responsible.
This is mostly based on mandatory training I had to go through while working for a US company. I am not a lawyer ;)
If embargoes were trivial to get around they'd be pointless. The intent of embargo laws are to as much as possible, within the full power of the US, prevent goods from getting to a certain country regardless of any other variable. Embargoes are pretty extreme actions, there are only a few targets for those in general and the embargo usually targets specific goods.
2. Canada has similar embargo laws on the books.
3. Canada has a multi-lateral extradition treaty with the US
4. The crime is considered serious with a maximum penalty (in the US) of up to 20 years in prison plus substantial monetary fines.
So she's accused of a serious crime in the US that's also recognized as a crime in Canada, and the countries have an extradition treaty.