In Ama v. Nwankwo  12 NWLR (Pt. 1049) 552 at 578, Rhodes-Vivour, JCA (as he then was) stated the position of the law relating to preliminary objection vis-à-vis the necessity of filing a supporting affidavit thusly: Preliminary objection strictly speaking deals with law. Consequently there is no need for supporting affidavit, but the grounds of the objection must be clearly stated. For example, objection that court process has not been complied with, suit/process is an abuse of process. When, as often happens a preliminary objection strays from law to facts of the case, the onus is on the party relying on the preliminary objection to justify the facts, and this can only be done by filing an affidavit. A preliminary objection may be supported by affidavit depending on what is being objected to. If the preliminary objection is on law, an affidavit is unnecessary, but if on facts an affidavit is mandatory (emphasis is this Court’s).
— B.B. Kanyip J. FG v. ASUU (2023) – NICN/ABJ/270/2022