> I thought those were on very solid ground commonly used by past administrations

No, Section 122 tariffs have never been used prior to Trump turning to them after the Supreme Court decision striking down the IEEPA tariffs, and, the states suing the Administration argue, the explicit sole statutory purpose for which they were allowed in the 1974 law creating the power can only possible to exist under a fixed-exchange-rate monetary system, which the US has not had since 1976.