Canada's immigration law does not place any restrictions on dual citizenship. Their liberal stance on dual citizenship is unique among nations. While most nations afford their citizens the right to dual citizenship, there are limits placed upon the exercise of certain rights. For example, to be naturalized as a United States citizen, a person must take an oath to renounce all previous national or state allegiances. In other countries, dual citizenship might be restricted based on age, occupation or language fluency. Because Canada has no restrictions on dual citizenship, and because its immigration laws are relatively open, the country has become home to many diverse and well-entrenched immigrant communities.