The Section 232 steel/aluminum tariffs are in place for some countries but not all, as exemptions are under negotiation. A few countries are still talking with the Trump administration about this, but others (Argentina, Brazil, South Korea, and possibly Australia but I'm not sure) have gotten out of the tariffs by agreeing to replace them with quotas. Here's how USTR explained the arrangement with South Korea: "U.S. negotiations with Korea have resulted in a satisfactory alternative for addressing U.S. national security concerns with respect to steel imports. ... Korean imports of steel products into the United States will be subject to a product-specific quota equivalent to 70% of the average annual import volume of such products during the period of 2015-17. This will result in a significant reduction in Korean steel shipments to the United States."
While some details are lacking, these agreements on steel/aluminum quotas almost certainly violate Safeguards Agreement Article 11.1(b), which provides:
(b) Furthermore, a Member shall not seek, take or maintain any voluntary export restraints, orderly marketing arrangements or any other similar measures on the export or the import side.3,4 These include actions taken by a single Member as well as actions under agreements, arrangements and understandings entered into by two or more Members. Any such measure in effect on the date of entry into force of the WTO Agreement shall be brought into conformity with this Agreement or phased out in accordance with paragraph 2.
3 An import quota applied as a safeguard measure in conformity with the relevant provisions of GATT 1994 and this Agreement may, by mutual agreement, be administered by the exporting Member.
4 Examples of similar measures include export moderation, export-price or import-price monitoring systems, export or import surveillance, compulsory import cartels and discretionary export or import licensing schemes, any of which afford protection.
I'm not sure exactly what kind of measure the steel/aluminum quotas are, but "voluntary export restraints" or "similar measures" are probably good descriptions.
But there is also Article 11.1(c), following directly after Article 11.1(b) but seeming to apply more broadly, which says:
(c) This Agreement does not apply to measures sought, taken or maintained by a Member pursuant to provisions of GATT 1994 other than Article XIX, and Multilateral Trade Agreements in Annex 1A other than this Agreement, or pursuant to protocols and agreements or arrangements concluded within the framework of GATT 1994.
It's pretty clear that "provisions of GATT 1994 other than Article XIX" includes GATT Article XXI, so it's easy to imagine the U.S. invoking Article XXI/Article 11.1(c) if the steel/aluminum quotas were challenged as violations of Article 11.1(b).
But what if it were not the U.S., but the other party to the VER, that is the subject of the WTO complaint? Just for fun, let's say that the EU challenges the South Korea - U.S. quota through a complaint against South Korea, rather than against the U.S. Could South Korea point to Article XXI/Article 11.1(c) as a justification? South Korea's national security is not at issue here, right? Or could South Korea invoke Article XXI/Article 11.1(c) based on the claimed national security interests of the U.S.?