Same way he's getting the executive to (apparently) dismantle federal departments.

With no legal precedent supporting him but absolutely no resistance from the branches of government meant to keep him in check.

He can simply take all pharma manufacturer portfolio off the medicare schedule, for example. That's what I would do, and it would be the right lawful move.

On the side, he may open the door for generic substitutes as well from CAN etc.

A simple price directive would be set at the same time, without any negotiation:

The price US medicare will pay will only be the average price for each drug, in all OECD countries.

Same way he created tariffs.

Wrong. Congress granted the Presidency an almost limitless power to levy tariffs in the early 1900s. It has no such power to change the tax laws.