A layered legal inheritance
Nigerian law draws on four coexisting sources rather than a single tradition: the Constitution and legislation enacted under it, received English common law and equity, customary law specific to individual ethnic communities, and Islamic (Sharia) law. Academic surveys of the system typically enumerate these as six formal sources once the Constitution, ordinary legislation, and judicial precedent are counted separately from the customary, English, and Islamic strands, since each operates through its own courts, its own rules of validity, and its own historical route into Nigerian practice S1. No single source displaces the others outright; instead the Constitution sits above all of them and allocates which body of law applies to a given dispute, a given place, or a given set of parties S1S2
The common law inheritance
English law entered Nigeria as what legal scholars call a "reception" rather than an imposition negotiated after independence: colonial-era legislation extended English common law, the doctrines of equity, and English statutes of general application as they stood in England on 1 January 1900 to Nigerian territory, and any English statute already applied to Nigeria before independence on 1 October 1960 remains part of Nigerian law today unless a Nigerian legislature has since repealed or replaced it S1. This reception explains why Nigerian contract, tort, and company law still track English legal concepts closely, and why Nigerian courts continue to cite pre-1960 English case law as persuasive or, in some unrepealed areas, binding authority S1. Since independence, the National Assembly and the 36 state Houses of Assembly have layered their own legislation on top of this inherited base, and the decisions of Nigerian courts themselves — arranged in the hierarchy described in nigeria court hierarchy — now form a body of binding domestic precedent S1
Customary law and its limits
Customary law is not one body of rules but hundreds, each specific to an ethnic community or locality and covering matters such as marriage, inheritance, land tenure, and chieftaincy; because it is mostly unwritten, its content is proved in court as a fact rather than looked up as a fixed text S1. Colonial and post-colonial law imposed a single check on every customary rule before a court will enforce it: the rule must not be "repugnant to natural justice, equity and good conscience," a validity test the British colonial administration also used to strip harsher penalties out of the pre-independence criminal law of the north S3. Disputes governed by customary law are heard first in Customary Courts created by state law, with a final appellate check available in a state's Customary Court of Appeal where one exists, as set out in Chapter VII of the 1999 Constitution S2S4
Islamic law's place in the system
Islamic law has operated in what is now northern Nigeria as a distinct, written legal tradition since well before the colonial period, tracing its authority to the Qur'an, the Sunna, and the interpretive traditions of Islamic scholarship, predominantly the Maliki school followed across West Africa S3. Colonial administrators retained Sharia-derived Native and Area Courts but confined their jurisdiction to personal status matters — marriage, divorce, inheritance, and guardianship among Muslims — while criminal matters were routed through the Penal Code for Northern Nigeria; this personal-status jurisdiction, run through what the Constitution now calls Sharia Courts of Appeal, has continued without interruption since long before 1999 S3S4. It was only from 2000 that a group of northern states began extending Sharia to criminal law by state statute, a distinct and more recent development covered in full in sharia in northern nigeria S3
The Constitution as supreme law
Section 1 of the 1999 Constitution — discussed in detail in nigerian constitution — declares the Constitution supreme over all other law in Nigeria and voids any inconsistent enactment to the extent of the inconsistency, a provision that in principle subordinates common law, customary law, and Sharia alike to its terms S3S4. In practice, disputes over how far that supremacy reaches have been sharpest around Sharia's extension into criminal law, since the Constitution's own text gives state Sharia Courts of Appeal jurisdiction only over "civil proceedings involving questions of Islamic personal law," leaving the constitutional basis for criminal Sharia courts to rest instead on the states' general law-making powers rather than on the sections naming Sharia courts directly S4. That unresolved question, along with the practical operation of the courts on all sides of it, runs through the companion articles on nigeria court hierarchy and sharia in northern nigeria S3S4
How the systems interact in practice
Which body of law and which court a case reaches depends on subject matter, the parties' faith, and geography rather than any single national code. A commercial dispute in Lagos proceeds through state or federal High Courts applying statute and common law; a land or marriage dispute rooted in local custom may go to a Customary Court; and a Muslim litigant in one of the twelve northern states with a Sharia penal code may face a Sharia court on a criminal charge that would be tried under the ordinary Criminal Code elsewhere in the federation S3. Nigeria's federal structure — described in federal structure of nigeria — is what allows this variation to exist lawfully across states while a single Constitution and a single apex Supreme Court, detailed in nigeria court hierarchy, ultimately sit over every strand of the system S2S4