When a choice of law issue arises, who decides: the parties (i.e., party autonomy) or the adjudicator? If the adjudicator decides, by what rules will the decision be made? As Catherine Walsh described in her 2010 Rand Lecture, party autonomy has been a flashpoint in discussions of domestic choice of law regimes. Over the past few decades, party autonomy has generally expanded, but a variety of limitations remain. If an adjudicator automatically applies the law or rules of law chosen by the parties, it would seem that their rights and interests have been protected. However, acceding to contractual choices of law may harm third parties or contravene the public policy of a country. Accordingly, courts have restricted party autonomy in choice of law. The advisability of such restrictions has led to deep philosophical debates about the interests that choice of law should serve and to earnest discussions of the proper scope of party autonomy. Party autonomy may be on the march, but it continues to face opposition.