The extraordinary recent increase in rates of cohabitation and non-marital birth presents a major challenge to traditional family law principles, and the legal rules governing cohabitation are thus among the most hotly contested areas of family law and policy today. In many nations, courts, legislatures, and law-reform bodies are "reinventing" common law marriage, seemingly without any sense of its history, doctrinal development, or limitations.

The current law surrounding common law marriage is extremely complex. Professor Goran Lind has undertaken the demanding task of writing the most...