The legal system in Burundi is a Civil law system. Having been colonised by Belgium, Burundi inherited the Belgian civil law. It applied positive law: all legislation, including the constitution, is codified. According to article 48 of the constitution, the constitution is the supreme law and any law that does not comply with the constitution is null and void. 

However, although the constitution does not mention Customary law, it is important to note that some laws, although very few, apply certain customary norms as a way of filling in gaps within the law. 

For example, Article 444 of Law n°1/13 of 9 August 2011 revising Burundi's land code states: “….Marshland is governed by customary law and cannot be registered.”

Also, Article 126 Decree-Law No. 1/024 of 28 April 1993 reforming the Family Code provides: “…the following are deemed to be dependent on the conjugal community unless proven otherwise by a legal, conventional or customary provision: - land acquired by devolution ...”