Suing a foreigner in Colorado can mean serving the complaint on a defendant in another country. The UN Convention on Service Abroad, through CRCP 4(d), offers one method for international service. But it is not the only one. In this original proceeding under Rule 21, the Supreme Court offers a rare interpretation of the relationship between international service under CRCP 4(d), and substitute service under CRCP 4(f). The trial court permitted substitute service on the defendant, who lived in Mexico, via his sister, who lived in Colorado, under CRCP 4(f). The defendant claimed that he must be served personally in Mexico under CRCP 4(d) and the Convention. The Court held those methods apply only when documents are “transmitted abroad.” None were because the defendant was served locally via his sister. Accordingly, service under CRCP 4(f) was sufficient and Constitutional.