Chapter 6, Domestic Partnerships, like many other parts' of the ALI Principles of the Law of Family Dissolution, functions as a set of default rules. Under the ALI Principles for domestic partnerships, therefore, if the parties meet state presumptive requirements for domestic partnerships and have not otherwise contracted, the rules of Chapter 6 apply. Usually, law sets default provisions to 1) what most parties would want; or 2) to what will promote efficiency. I will discuss these two concepts in turn, illustrating how the ALI domestic partnerships provisions satisfy neither ex ante hypothetical bargaining nor efficiency criteria, and thus that Chapter 6, which purports to set default rules, breaks from this usual pattern. In fact, instead of doing what most parties would want or what is good for broader society, Chapter 6 both over- and undershoots its target.