Right of asylum (or political asylum) is an ancient juicial notion, under which a person persecuted for political opinions or religious beliefs in his or her own country may be protected by another sovereign authority, a foreign country, or Church sanctuaries (as in medieval times). Political asylum should not be mistaken with modern refugee law, which rather deals with massive influx of population, while the right of asylum concerns individuals and is usually delivered in a case-to-case basis.[verification needed] However, the two may somehow overlap, since each refugee may demand to be accorded on an individual basis political asylum. This right has its roots in a longstanding Western tradition—although it was already recognized by the Egyptians, the Greeks and the Hebrews—Descartes went to the Netherlands, Voltaire to England, Hobbes to France (followed by many English nobles during the English Civil War), etc. Each state offered protection to foreign persecuted persons. However, the development in the 20th century of bilateral extradition treaties has endangered the right of asylum, although international law considers that a state has no obligation to surrender an alleged criminal to a foreign state, as one principle of sovereignty is that every state has legal authority over the people within its borders.