It's important to realize that this varies a lot between countries. The rule we're discussing is from the English common law tradition, but contracts where only

It's important to realize that this varies a lot between countries. The rule we're discussing is from the English common law tradition, but contracts where only one of the parties has any obligations are legal in the many countries which use the civil law system with origins in mainland Europe. In North America, the main places where the civil law system is in use for these types of matters are the Canadian province of Quebec, the US state of Louisiana, and Mexico. Worldwide, the predominant system varies by geography, but the civil law system is actually more prevalent globally than the common law system.