According to the Shariah, Muslims living in the West (or other non-Muslim states) are essentially visitors from the perspective of the sacred law. The standard definition amongst Muslim scholars for the Abode of Islam (Dar al-Islam) was those lands where the Shariah reigns. Muslims outside that space reside in lands and countries as guests of whatever legal or religious system reigns there. If the law of the land were to prohibit Muslims from carrying out a duty required by the Shariah, such as prayer, or require them to do something clearly forbidden in Islam, such as drinking alcohol, the standard opinion amongst classical Muslim scholars was that Muslims could no longer reside there (a second opinion was that they should remain so that the religion of Islam would not vanish there). Otherwise, Muslims must respect the law of the land. Their decision to reside in those lands represents their agreement to a contract with the governments ruling them. As the Quran commands Muslims, “be true to your agreements” (Quran 5:1), and as the Prophetﷺ taught, “Muslims are bound by the conditions [of their agreements].” The Shariah continues to govern Muslims’ private worship and whatever areas of law the local system leaves open (such as contracts, inheritance and marriage in the US), but Muslims must respect and abide by the restrictions, duties and regulations placed upon them.
— Jonathan Brown is the Alwaleed bin Talal Chair of Islamic Civilization at Georgetown University