Extradition — Conditions — Allegation that lives of accused would be in jeopardy if they were extradited — Whether matter for Executive or courts

Extradition — Of nationals — Accused claiming United States nationality — Discretion of Executive whether or not to surrender nationals — Mexico-United States Extradition Treaty, 1899, Article IV — Government of Mexico allegedly declining to extradite Mexican nationals — Whether precluding United States from extraditing United States nationals to Mexico — Whether matter for Executive or courts

Extradition — Political offence — Definition — Requirement that offence be committed in course of political upheaval — Political motivation alone insufficient

Extradition — Procedure — Evidence — Extent to which accused is entitled to challenge evidence in extradition proceedings — Scope of judicial review of determination by magistrate

Treaties — Interpretation — Subsequent practice — Practice regarding provision in extradition treaty — Significance of adoption of similar provision in new treaty — The law of the United States