The thing being called a national security risk is a lack of domestic production capability. No one is saying Canadian steel is sabotaged or something.

Yes, obviously- but one of our closest allies shorting us on steel supplies in a time of crisis has never happened, while espionage from China-produced tech is happening right now. Which should be our priority?

Though it is, because it happened with Kobe Steel. (Not saying Canada specifically.)

They faked the data on what it could handle; and with things such as aircraft, lives depend on that data.

That isn't a Japanese steel concern though, that's a steel manufacturing concern. U.S. Steel could do the same thing.

But they are saying that Canada would cut us off from their steel production in a time of need, which is a pretty absurd assessment of the situation.

I love a good Trump bashing moment as much as the next guy, but this is inaccurate. The DoD has stringent requirements and quality control procedures in place for their chip procurement. Not to say they couldn't be improved, but the DoD has been aware of this threat for a while, and seems to be mitigating the risk fairly well.

Also, as far as I understand the argument, it goes beyond "Canadian steel is a national security risk". A couple of years ago, Mexico was caught laundering $2B of Chinese aluminum to avoid US taxes.

http://fortune.com/2016/09/09/chinese-aluminum-giant-is-tied...

The theory, from the Trump crowd, is that Canada is also engaged in similar shady dealings with China. If true, that would put the US at risk.

Even if true, how does that make it a national security risk?

If the source is China, in a hostile period they might stop sending it. But according reportings I have read, the US DoD only uses about 0.5% of steel in the US, and only ~30% of US steel is imported.

Their argument is that you need strong domestic steel industry to build tanks, ships, etc, in case of war. Not saying I'm agreeing with it just pointing out the stated rationale behind the tarrifs.

The concern was the depression in prices was cratering local high-quality smelting capacity.

However, the DOD issued a memo (penned by Mattis iirc) indicating that there was no supply related concerns. The lack of aluminum used to justify the tariffs was in fact just the result of the LME's anti-market-tampering rules creating an incentive for metals traders to stockpile the material in private stores rather than in LME warehouses.

There was a nice article about this yesterday, but I don't have the link.

It doesn't. They claimed that so they could enact the tariffs, otherwise it would be a WTO illegal tariff. I think Canada/others are arguing that it is not a security risk and therefore is indeed an illegal tariff. This is what I remember from some articles. Please correct/elaborate.

Maybe because it undermines fundamental US business interests, and therefore wellbeing? If so it still seems like a stretch to me. Doubtful we'd have no where else to source steel if war or disaster struck.