The United States allows dual citizenship, meaning individuals can hold U.S. citizenship along with citizenship of another country. U.S. law does not require naturalized citizens to renounce their previous citizenship, though some countries may require renunciation. Dual citizens owe allegiance to both countries and must comply with the laws of both, including potential tax obligations and military service requirements. U.S. citizens, including dual citizens, must use a U.S. passport when entering or leaving the United States.