When can one requirement override another?

I argue that any theory of moral obligation must be able to explain two things: why we cannot be thrust into a moral dilemma through no fault of our own, and why we can get into a moral dilemma through our own negligence. The most intuitive theory of moral obligation cannot do so. However, I offer a theory of moral obligation that satisfies both of these criteria, one that is founded on the principle that if you are required to do something, then you would be blameworthy for failing to do it. I conclude by relating these results to the current literature on moral dilemmas.