The U.S. has issued a reply to the World Trade Organization (WTO) in response to the complaint submitted by Canada on March 4, 2025, see Trade News article: https://cscb.ca/en/article/canada-initiates-wto-dispute-complaint-regarding-us-steel-and-aluminium-duties
Link to the WTO site: https://www.wto.org/english/tratop_e/dispu_e/cases_e/ds634_e.htm
They state that the tariffs imposed against Canada are "issues of national security are political matters not susceptible to review or capable of resolution by WTO dispute settlement. Every Member of the WTO retains the authority to determine for itself those measures that it considers necessary to the protection of its essential security interests, as is reflected in the text of Article XXI of the GATT 1994.".
Despite that, the U.S. will accept Canada's request to enter into consultations on a mutually convenient date.
Please click this link for the full response / WTO pdf document: https://cscb.ca/en/media/document/us-reply-wto-complaint