The position of the law is that where a statute declares a contract or transaction between parties not only void but also imposes a penalty for violation, that contract or transaction is illegal ab initio. However where the legal sanction is merely to prevent abuse or fraud and no penalty is imposed for the violation of the provision of the statute, the violation is merely voidable and not illegal. See Solanke v. Abed (supra); Oil-field Supply Centre Ltd. v. Johnson (1987) 2 N.W.L.R. (Pt. 58) 265 and Ibrahim v. Osim (1988) 3 N.W.L.R. (Pt. 82) 257 and Pan Bishbilder (Nigeria) Ltd. v. First Bank of Nigeria Ltd (2000) 1 N.W.L.R. (Pt. 642) 684 at 693 where Achike JSC (of blessed memory) clearly stated the position of the law:- “Permit me to digress generally on illegality. It is common ground that illegality and voidness of the loan contract between the parties is the main subject matter of controversy in this appeal. Definition of the term illegal contract has been elusive. The production of clarity of the classification of illegality appears to be almost confounded and rendered intractable primarily because – writers and the Judges have continued to use the terms ‘void’ and ‘illegal’ interchangeably. Halsbury’s Laws of England (3rd ed. vol. 8 p. 126 para. 218) states that – ‘A contract is illegal where the subject matter of the promise is illegal or where the consideration or any part of it is illegal.’ Without getting unduly enmeshed in the controversy regarding the definition or classification of that term, it will be enough to say that contracts which are prohibited by statute or at common law, coupled with provisions for sanction (such as fine or imprisonment) in the event of its contravention are said to be illegal. There is however the need to make a distinction between contracts that are merely declared void and those declared illegal. For instance, if the provisions of the law require certain formalities to be performed as conditions precedent for the validity of the transaction without however imposing any penalty for non-compliance, the result of failure to comply with the formalities merely renders the transaction void, but if a penalty is imposed, the transaction is not only void but illegal, unless the circumstances are such that the provisions of the statute stipulate otherwise. See Solanke v. Abed & Anor. (1962) N.R.N .L.R. 92, (1962) 1 S.C.N.L.R. 371 and P. Kasumu & Ors. v. Baba-Egbe 14 WACA 444.”
— Mohammed, JSC. Fasel v NPA (2009) – SC.88/2003