It's not at all difficult to prove copyright infringement of a paper submitted for peer review. The editors will have a copy of the paper and its submission wil

It's not at all difficult to prove copyright infringement of a paper submitted for peer review. The editors will have a copy of the paper and its submission will be date stamped in the peer review submission system. That's simply not the issue here. What happened is the reviewer submitted substantially the same manuscript to another journal, hoping no one would notice. The difficulty isn't in remedying or proving copyright infringement, but noticing it!