More legal
In theory, if Apple chose to charge individually for HD movies, the same way iTunes sells its music, and simply transferred them using a Bittorrent file sharing model, there would be virtually no legal problem. However, because Apple can not expect all of its customers or non-customers to be honest, upright individuals the real world model of this problem is a bit trickier.
If Apple chose to use Bitorrent for transferring video content, which I would not suggest, they may have issues with vicarious copyright infringement. However, I would argue that would likely not be libel for vicarious infringement if they chose to use DRM protection. Obviously by enlisting protection for the materials transferred through the Internet (identical to how they currently transfer songs) Apple would appease groups like the MPAA. On the other hand with strict regulation of how their customers could use their newly purchased videos, I think it may encourage piracy such as creating illegal copies prior to transfer, cracking DRM protection or even hacking into the transfer period to obtain copies. This seems like something that may eventually create a copyright or licensing problem for Apple and is why I suggest they avoid the issue altogether. Overall it is difficult to speculate if in fact Apple would be in the clear if a lawsuit came to head due to the lack of legal precedent in this area.