This is as good a starting place as any. https://ilr.law.uiowa.edu/print/volume-101-issue-2/copyright...

This might sound stupid, and maybe it is, but that’s the state of law right now. It’s possible somebody will drag out a big slam dunk case that overturns much of this or that new laws will be passed… but right now (as far as I can tell) Copilot looks pretty legal.

(Of course, talk to your legal counsel, this may vary be region, etc.)