They're both to blame. Studio Canal insisted on a licensing agreement that works this way, and Sony agreed to it to sell their content.
For Sony, the correct move here would have been to not list Studio Canal titles in the first place, and put out a very public statement saying that they aren't being listed until Studio Canal agrees to make purchased licenses perpetual as they should be.
> Both to blame
IANAL but I think the US law approach is to rely on chaining, so the #1 blame is on Sony until Sony proves it isn't.
1. Consumers who were damaged sue Sony for damages.
2. If Sony loses, Sony sues Studio Canal for damages.
3. If Studio Canal loses... ?
Correct. In theory, Sony should have warranted that they have the rights to sell the thing the way they sold it. If they didn't have the rights to sell a movie perpetually, then that's on them.
They don't need the rights to sell a movie perpetually, just the rights to sell perpetual movies.