Amendments not like the US Constitution amendments, but including ones that rewrite the whole of the constitution. That's how they've gone back and forth between a presidential system and a parliamentary system, and frankly between a semi functioning democracy and an outright dictatorship.
The point is, they're not simply keeping the collective bargaining rights because they're too difficult to change since the 1940s. The ROK have no qualms making massive changes to the very core of their constitution, including rewriting what got in the way of a corporatist dictatorship under Park.
