Word of Smith’s plan reached the Owens family. The specific mechanism by which this happened — whether through direct communication with Mason or through community information networks — is not detailed in the surviving sources. What is established is that Robert Owens took action promptly. He went to the Los Angeles County Sheriff. He obtained, or helped obtain, a writ of habeas corpus requiring Smith to produce before a judge the people he was proposing to take to Texas.
The writ was served on Smith when his wagon train was at or near Cajon Pass, in the mountains northeast of Los Angeles. This was essentially the last moment at which a California court could exercise jurisdiction over the matter: once Smith crossed into Nevada Territory and headed southeast toward Texas, the California courts would have had no reach.
Owens assembled a group that sources describe as a posse — his sons and ranch workers — and accompanied or coordinated with the sheriff’s representative in physically stopping the wagon train. The enslaved people were taken into the sheriff’s custody and conveyed to Los Angeles. Smith was required to appear before Judge Hayes.
The intervention was not legally complicated in its basic mechanism: a habeas corpus petition was a standard legal tool for challenging unlawful detention or removal. What was unusual was the community organization behind it and the speed with which it was executed. The window for effective action was narrow — the wagon train was leaving California — and the people who intervened had the resources and the relationships to act within that window.