Proclamation 58—Warning to United States Citizens Against Participating in an Unlawful Invasion of Mexico
By the President of the United States of America
Whereas there is reason to believe that a military expedition is about to be fitted out in the United States for the purpose of invading the Mexican Republic, with which this country is at peace; and
Whereas there is reason to apprehend that a portion of the people of this country, regardless of their duties as good citizens, are concerned in or may be seduced to take part in the same; and
Whereas such enterprises tend to degrade the character of the United States in the opinion of the civilized world and are expressly prohibited by law:
Now, therefore, I have issued this my proclamation, warning all persons who shall connect themselves with any such enterprise in violation of the laws and national obligations of the United States that they will thereby subject themselves to the heavy penalties denounced against such offenses; that if they should be captured within the jurisdiction of the Mexican authorities they must expect to be tried and punished according to the laws of Mexico and will have no right to claim the interposition of this Government in their behalf.
I therefore exhort all well-disposed citizens who have at heart the reputation of their country and are animated with a just regard for its laws, its peace, and its welfare to discountenance and by all lawful means prevent any such enterprise; and I call upon every officer of this Government, civil or military, to be vigilant in arresting for trial and punishment every such offender.
Given under my hand the 22d day of October, A. D. 1851, and the seventy-sixth of the Independence of the United States.
By the President:
Acting Secretary of State.
Millard Fillmore, Proclamation 58—Warning to United States Citizens Against Participating in an Unlawful Invasion of Mexico Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/201117