In October, 1851, Samuel Curtis gave his federal grand jury a definition of treason (PDF). He expected, in a Boston where antislavery Americans had lately rescued a few fugitive slaves from those who aimed to steal them back to slavery, that the jury might need to know. Curtis laid out a three point test: The accused must conspire. That conspiracy must involve obstructing the enforcement of a law of the United States. The conspiracy must then use force to that end. All of these applied to Bostonians who had saved enslaved Americans from recapture. Together, these things constituted levying war against the United States. They might, depending on how one read them, apply to the free state movement in Kansas as well.
Curtis did better than nineteenth century bullet points. He wanted his jurors to understand the law thoroughly and so gave a further explanation that runs to about a page of printed text. That section opened with an important qualifier:
It is not enough that the purpose of the combination is to oppose the execution of a law in some particular case, and in that only. If a person against whom process has issued from a court of the United States, should assemble and arm his friends forcibly to prevent an arrest, and in pursuance of such design, resistance should be made by those thus assembled, they would be guilty of a very high crime, but it would not be treason
In a Bostonian context, this means one could throw together to rescue Shadrach Minkins or Anthony Burns and not commit treason. Over in Kansas, Samuel Jones had a warrant to arrest Jacob Branson. He had that warrant under the authority of the federally-constituted territorial government. I don’t know if a territorial court operating under that law counts as a court of the United States rather than one of Kansas Territory, but even granting Jones the point Branson and his rescuers might fall short of Curtis’ definition of treason. They opposed the execution of the law, by force, in one particular case.
However, if the individuals combined
forcibly to prevent any person from being arrested under that law, and with such intent, force is used by them for that purpose, they are guilty of treason.
Here Samuel Newitt Wood and company get into deeper trouble. They as much as told Jones that they would rescue anybody he came after with a warrant. Though the people of Lawrence tried to disavow the rescue of Branson, they had made rhetorical pledges to resist Kansas’ laws too. Their resistance didn’t extent to force, yet. They took pains to emphasize they resisted the laws of Kansas, not the United States. Charles Robinson, at least, understood resisting Wilson Shannon by force as resisting federal authority. Whether he meant that as a precise legal judgment or just a recognition of how Shannon might treat things, the ambiguity remains.
One might argue that the resistance to one law doesn’t really count, just as resisting on behalf of one person doesn’t count. Curtis anticipated the argument and would have nothing of it:
The law does not distinguish between a purpose to prevent the execution of one, or several, or all laws. Indeed, such a distinction would be found impracticable, if it were attempted. If this crime could not be committed by forcibly resisting one law, how many laws should be thus resisted to constitute it? Should it be two, or three, or what particular number short of all? And if all, how easy would it be for the worst of treason to escape punishment, simply by excepting out of the treasonable design, some one law.
The judge has a point. If the Army of Northern Virginia scrupulously held to the fugitive slave law, and they did so enthusiastically when they had the chance in Pennsylvania, then that hardly made them innocent of treason. Robert E. Lee commanded, among other things, the largest slave patrol in American history.