Ever since humans have been on Earth, there has been migration. And with migration, come transnational attachments, sometimes creating phenomena which have been called 'diasporas' since the Septuagint. Although traditionally applied only to some paradigmatic cases, particularly the Jewish, Armenian or Greek diasporas, in recent times the term has come to be used more broadly to cover new situations arising from the current globalized world. This thesis addresses legal instruments used by European states to engage with populations abroad that they consider diasporas. Traditionally ignored by legal scholarship, diasporas had been often addressed from the point of view of the so-called 'host country'. This thesis takes the perspective of the 'motherland', and how 'diaspora laws' respond to the diasporic phenomenon. After defining key concepts, such as 'diaspora' itself, the thesis identifies five categories of diaspora laws. Building on this typology, the thesis takes a double approach. The first is a comparative legal take on the diaspora laws of four EU Member countries: Hungary, Ireland, Italy, and Spain, selected because of the different characteristics of their diasporas. By analyzing the laws of these countries, the thesis finds that diaspora legislation does not necessarily respond to diaspora characteristics, but rather too often to partisan interests in the state of origin. The second part of the thesis looks at several aspects of diaspora laws which may clash with established principles of international law. In particular, the thesis considers jurisdiction, nationality, and other principles like pacta sunt servanda, nondiscrimination, and non-intervention and friendly relations. The thesis finds that while most diaspora laws do not clash with these principles, several issues could arise, in particular with regards to friendly relations. The main conclusion of the thesis is thus that more international cooperation is desirable in relation to diasporas.