Which principle protects citizens from the government interfering with personal beliefs and practices?

The principle that protects citizens from government interference in their personal beliefs and practices is freedom of religion. This concept is enshrined in the First Amendment of the U.S. Constitution, which guarantees that individuals have the right to practice their religion freely without government intervention. This principle not only allows citizens to hold and express their religious beliefs but also prohibits the government from establishing a national religion or favoring one religion over another, thereby ensuring a separation between personal faith and governmental authority.

Federalism refers to the distribution of power between the national and state governments, which does not directly address personal beliefs. The separation of powers is a governance structure that divides responsibilities among the legislative, executive, and judicial branches, aimed at preventing the concentration of power. Popular sovereignty is the doctrine that the government's power derives from the consent of the governed, which primarily focuses on the authority and rights of the populace regarding governance, rather than individual belief systems.

Freedom of religion specifically emphasizes the individual's right to believe and practice according to their own faith, making it the most appropriate answer to the question regarding protection from government interference in personal beliefs.