Sometimes, of course, the publishers of academic papers would very much like to keep them behind their internet pay-stations, where they can charge people to see them or download them. So, they do sometimes exercise their influence in that direction. But when there is a moral purpose in wider circulation, there is a good deal of tolerance of such wider circulation in Europe--in my understanding of the matter.
In any case, it would seem to be a civil conflict between publisher and author and not a matter of criminal law. Publishers are usually pretty tolerant.
No, if the journal forbids it. This is why RG always asks you a question about the storage mode (private or public) when you want to add the full text.