The action, which Mr. Rubio spoke about during a brief visit to Quito, the capital of Ecuador, is the latest in a series of terrorist designations of criminal groups in Latin America undertaken by the Trump administration.
The State Department is designating Los Tiguerones as both a foreign terrorist organization and a specially designated global terrorist. Those formal labels give the U.S. government legal tools to try to freeze or seize assets linked to the group that are in the U.S. financial and banking systems.
While terrorism designations by the State and Treasury departments can have financial consequences, they do not give the U.S. military any legal basis to carry out operations against groups added to the list. The Trump administration has nevertheless emphasized such designations when announcing military actions against them.