Zakirai v. Muhammad  17 NWLR (Pt. 1594) 181 at 230-231, paras. G-D, per Augie, JSC:
“His [The Appellant’s] objection was a complaint against the competence of the trial court to entertain the suit because the originating summons was not endorsed or marked as required by the said Act and Rules, which touches on the procedural rules that got parties to the court, and nothing whatsoever on the facts that led to the cause of action or substance of the suit filed by the first respondent. Any defect amounted to a mere irregularity that can be waived by the parties… In this case, the Appellant entered a conditional appearance and also filed a counter-affidavit [to the Originating Summons], which means he waived the irregularity that he complained of, and had submitted to the jurisdiction of the court.”
The Court reasoned that while substantive jurisdiction of the court cannot be waived, a party can waive an issue relating to procedural jurisdiction of the court. In effect, the Court was of the view that the issue relating to the endorsement and marking of an originating process for service outside jurisdiction as provided for by the Sheriffs and Civil Process Act is an issue touching on the procedural jurisdiction of the court and thus can be waived.
The above position appears to run contrary to the Supreme Court position in the case of Owners of MV “Arabella” v. N.A.I.C.  11 NWLR (Pt. 1097) 182 where the Court held that such irregularity is not a mere one that can be waived and that it is immaterial that the defendant had taken steps. It was held there that failure to comply with the Act is fatal as it robs the court of jurisdiction to determine the suit.