How Would a Free Society Deal with Less Proximate Causes of Injuries?

Via lowercase liberty, I came across this article about a libertarian theory of punishment predicated on “proportionality”: http://bkmarcus.com/blog/2007/03/punishment-and-proportionality

What is it about the concept of proportionality as the core principle for determining punishment that makes it particularly “libertarian”? The author discusses some other theories and finds that their application is less consistent with libertarian principles than a system predicated on proportionality. In my view, overall freedom is enhanced through the employment of principles that are simple, predictable and require less in the way of an administrative apparatus.

An issue not addressed in the article, but related and on my mind lately, involves the mechanism for deciding punishment or compensation in the case of multiple wrongdoers and in the case of wrongdoing that is less proximate but nonetheless causative of injury. Is there necessarily a uniquely “libertarian” set of principles to guide us in making these kind of determinations?

There are many instances where the contribution of an action or inaction to causation of an injury can be factually established but where it is does not seem reasonable to attach moral or legal blame. If I feed the ducks in a pond, and these same ducks cause a plane crash, which they would not have done had I not delayed them with duck chow, I may be said to have contributed to the crash, but it does not seem reasonable to blame me for the crash or to require me to compensate the victims.

On the other hand, if I manufacture an aircraft engine part and use substandard materials such that its likelihood of failure is increased, and its failure subsequently contributes to a plane crash, it seems reasonable to bring me to account. The difference, where each action is remote from the injury and where there is no intent to cause injury, is the degree of foreseeability and the extent to which the actor has a duty to the injured party. Of course, opinions may vary as to what degree of foreseeability must be demonstrated before liability should attach. The same goes for duty.

At some point, an arbitrary assumption must be made as to what causal acts or failures to act warrant moral culpability or legal liability. This judgment will be, on the one hand, a moral one. On the other hand, it is related to the complexity and cost of the administrative apparatus designed to make the determination and dispense justice. Accordingly, you may find a remote cause morally objectionable yet be unwilling to maintain a system to apply coercion in the case of that same cause.

Is there a “libertarian” solution to this problem? Are the concepts of foreseeability and duty helpful?