Jack, I too was assuming that Tom wasn’t around. But what he would think about the whole thing is definitely an important issue. Within the conception of rights that I’m working with, Klemm “infringes” upon Tom’s right if Tom has the right that X be the case, and Klemm actively makes it so not-X is the case. Klemm “violates” Tom’s right if and only if he infringes upon Tom’s right and is morally blameworthy for doing so. So if Tom has the right that his cabin not be broken into, and Klemm breaks into his cabin, then he infringes Tom’s right. If we think that he is morally blameworthy for this, then we would say that he violates Tom’s right.
In assessing moral blameworthiness, it seems like we would want to focus only on the decision that Klemm made. Whether Klemm’s actions are morally permissible or impermissible would seem to depend on what Klemm should have done in the situation he faced. Accordingly, it seems difficult to say that Tom’s retroactive consent could determine whether or not Klemm acted wrongly. Klemm’s couldn’t have possibly known whether Tom would later offer his consent, and it seems like we would want to say that the rightness or wrongness of Klemm’s actions was determined at the time of the decision to act, not later.
I do think that it’s important to distinguish between issues like the appropriateness of compensation and those relating to moral blameworthiness, though they are surely related. Under some conceptions of law, we might want to say that Klemm should have to pay for the damage he did if Tom wants him to, whether or not what he did was morally blameworthy (these standards are generally based on a notion of “strict liability”). According to other views, Klemm would have to pay only if what he did was morally wrong (these standards are typically built around a notion of a “duty of care”). But this legal aspect is separate from the issue of whether or not Klemm would be justified in breaking in. This, I think, can most clearly be demonstrated by the obvious falsity of the statement, “Whether or not the rapist acted immorally depends on whether he is held accountable for the rape.”