Since the founding of this nation, Americans have relied on fundamental constitutional principles for the ultimate protection of their religious liberty. These guarantees have been extended to all persons in the United States, not just citizens. American nationals traveling or living abroad may discover, however, that religious freedom is not regarded as a fundamental right elsewhere. Although most nations do, at least in principle, adhere to the basic idea of freedom of religious belief and exercise, religious freedom may be denied either to a state's own citizens or to foreign nationals within its boundaries.
Bruce F. Howell,
Toward International Freedom of Religion: A Proposal for Change in FCN Treaty Practice,
U. Mich. J. L. Reform
Available at: https://repository.law.umich.edu/mjlr/vol7/iss3/7