Having set out why he thought the Neutrality Act so important, aside from his duty to execute the laws, Buchanan’s January 7, 1858 message to Congress continued to lay out the pertinent legal details. Neutrality laws went all the way back to the 1790s and the chief provisions of the original, Washington-era, law remained in the then-current version. What constituted a violation of the Neutrality Act?
The military expedition rendered criminal by the act must have its origin, must “begin,” or be “set on foot,” in the United States; but the great object of the law was to save foreign States with whom we were at peace from the ravages of these lawless expeditions proceeding from our shores. […] In order to render the law effectual, it was necessary to prevent “the carrying on” of such expeditions to their consummation after they had succeeded in leaving our shores.
This has been done effectually, and in clear and explicit language, by the authority given to the President under the eighth section of the act to employ the land and naval forces of the United States “for the purpose of preventing the carrying on of any such expedition or enterprise from the territories or jurisdiction of the United States against the territories or domain of any foreign prince or States, or any colony, district, or people with whom the United States are at peace.”
That certainly sounds like Walker’s expeditions. It also sounds like Narciso López’s and John Quitman’s expeditions against Cuba. All set out with the avowed purpose of overthrowing a country at peace with the United States. All began in the United States. All had logistical and financial support from within the United States. Walker, like López and Quitman, clearly broke the law.
Why then did Walker’s arrest provoke such controversy? Expansionists might not have loved how Zachary Taylor intercepted López and his expedition. They admired that effort at least as much as Walker’s and wanting to steal Cuba amounted to a tradition in the movement. Nicaragua, while certainly desirable, had not occupied their imaginations nearly as often. Whence came the outrage? Aside the increasing radicalism of the late 1850s and the usual partisan rhetoric, they had reason to think Paulding acted improperly.
Senator James Rood Doolittle (R-WI, by 1858 we have Republicans in the Senate) described Walker’s capture:
I understand the President of the United States to assume, as an undisputed fact, that this expedition, of which Walker was the chief, was set on foot within the jurisdiction of the United States to make war against Nicaragua, a Republic at peace with us; that it was well known to the Government of the United States that this expedition was about to be carried on against Nicaragua; that the leader of this expedition was arrested by officers of the United States, but was discharged upon giving bail in the insufficient sum of $2,000; that soon after his discharge, Walker, with his command, embarked on board the steamer Fashion, a vessel of the United States, and sailing under the flag of the United States, and entered San Juan; and under the very guns of the Saratoga, a vessel of war of the United States, lying in the waters of San Juan, he was permitted to land upon the soil of Nicaragua; that immediately after landing, he commenced, and was actually engaged in carrying on, a lawless warfare against the people and the Government of Nicaragua; and that while he was so engaged upon the shores of Nicaragua, Commodore Paulding arrived in the harbor of San Juan, in command of the flag-ship Wabash; that after he arrived there, he immediately ordered General Walker and his command to embark on board such vessels as he should designate, and compelled them to embark and return to the United States.
Walker sailed from the US with an illegal filibustering expedition. He reached Nicaragua, passing a US warship to do so, and and landed there. Paulding sent some boats and Marines to block the advance of Walker’s little army up the river it planned to use, then maneuvered his ships to block retreat, and trained cannons on Walker’s camp. Walker got the hint and surrendered himself.
This presents a real problem of international law. By what authority did Paudling arrest Walker on Nicaraguan soil? True, the filibuster broke American laws. But he no longer stood on American soil or in an American jurisdiction. Technically speaking, Paulding invaded Nicaragua, occupied its coast, blockaded its territorial waters, and as he had no legal authority within the nation kidnapped people from its shores at gunpoint. Whether or not Paulding exceeded his instructions, he clearly violated international law.
In the service of their political aims, the expansionists suddenly found themselves defending Nicaragua’s aggrieved sovereignty against a rogue military man.