Congress lawfully delegated some decisions to the executive, in 1934 - https://en.wikipedia.org/wiki/Reciprocal_Tariff_Act. They can undo that, if they want. I suspect they will, but only when it’s well beyond abundantly clear they need to.
Congress delegated almost all decisions to the Executive.
That’s how the system works given that legislation is high-level, often vague and sometimes riddled with errors. Congress sets the goals and Executive i.e. public sector makes the decisions about how to implement it.
