Despite increasingly forceful statements from a range of international human rights bodies and experts against the routine use of detention as a form of immigration control, detention continues to be a frequent response to violations of immigration laws and regulations, such as unauthorized entry or presence of non-nationals in a host country. This paper elaborates states’ obligations to provide effective alternatives to immigration detention for irregular migrants and asylum-seekers. It does not deal with alternatives to detention under criminal charge, or for national security or related reasons