It is generally agreed that the jurisdiction of courts in civil matters is territorial. Where therefore the court intends to assert its jurisdiction over a person not within its territory, certain criteria must be met. Section 97 of the Sheriffs and Civil Processes Act makes it mandatory that writ of summons meant for service out of a state must be endorsed to show that it is for service out of the state of issuance and in another state of the Federation. The leading cases on this provision are contradictory; while some cases tend to say that it is mandatory, others interpret it to be directory. This article probes into the leading decisions of the apex court on the issue and presents the view that whereas the provision is mandatory, non-endorsement will only render the writ voidable if raised as a preliminary issue by the party entitled thereto.