For someone who is supposedly trying to burnish his legacy, Bush is certainly going about it a strange way.
The idea that a president would veto a ban on torture is utterly shameful.
However, it also might create a vulnerability for an eventual war crimes prosecution should he ever be incautious enough to travel abroad. While he could never be realistically held to legal account in the U.S. for exercising his constitutional prerogative of a veto, it might be the kind of overt act that a foreign court would consider subject to prosecution under international law.
Considering that there's no statute of limitations for war crimes, Bush may find his foreign travels circumscribed.