> It would run into Takings Clause challenges

The incumbents would probably file lawsuits, but would they win?

If Congress can set copyright terms retroactively, why can't they set copyright terms retroactively?

What happens if they do the thing where you have to file for a renewal every year and the first 14 years are free and automatic, but then the renewal fee starts at $1000 and doubles for every year over 14?

> violate treaties the US has signed.

This is just an excuse the industry uses after bribing their way into some documents that can be renegotiated at any time. The US has been the ones pushing for this nonsense to begin with, so if they stopped, most other countries would be happy to enter into a different treaty. And the remaining ones would be the ones with the most to lose if they were the only ones to not sign onto the new agreement at the point when the US and most others pull out of the corrupt one.