The first main factor was the impact of a lawsuit of this nature on foreign relations:
Jesus Mesa Jr. and the parents of 15-year-old Sergio Adrián Hernández Güereca gave different accounts of what happened, with the parents claiming the teen and his friends were playing a game where they ran back and forth across the border, and Mesa claiming they threw rocks at him during an illegal border-crossing attempt. The Supreme Court's 5-4 ruling said that regardless of the circumstances, precedent regarding lawsuits against officers, known as "Bivens claims," does not apply to cross-border shootings.
In the 1971 opinion Bivens v. Six Unknown Fed. Narcotics Agents, the Supreme Court held that a person claiming they were unlawfully arrested and searched could bring a lawsuit under the Fourth Amendment, even if there was no statutory basis for it. In Tuesday's opinion, Alito noted the high standard of extending Bivens to a "new context" and gave several reasons why it was inappropriate in this case.
The court extending into this situation and dictating national security could undermine border security.
"A cross-border shooting is by definition an international incident; it involves an event that occurs simultaneously in two countries and affects both countries’ interests," Alito wrote. "Such an incident may lead to a disagreement between those countries, as happened in this case." The U.S. had determined that Mesa should not face criminal charges or be extradited to Mexico.
“To avoid upsetting the delicate web of international relations, we typically presume that even congressionally crafted causes of action do not apply outside our borders," the opinion said. “These concerns are only heightened when judges are asked to fashion constitutional remedies. Congress, which has authority in the field of foreign affairs, has chosen not to create liability in similar statutes, leaving the resolution of extraterritorial claims brought by foreign nationals to executive officials and the diplomatic process.”