"It will be sufficient to observe briefly that the sovereignties in Europe, and particularly in England, exist on feudal principles. That system considers the Prince as the sovereign, and the people as his subjects; it regards his person as the object of allegiance, and excludes the idea of his being on an equal footing with a subject, either in a court of justice or elsewhere. That system contemplates him as being the fountain of honor and authority, and from his grace and grant derives all franchises, immunities and privileges; it is easy to perceive that such a sovereign could not be amenable to a court of justice, or subjected to judicial controul and actual constraint. It was of necessity, therefore, that suability became incompatible with such sovereignty. Besides, the Prince having all the Executive powers, the judgment of the courts would, in fact, be only monitory, not mandatory to him, and a capacity to be advised is a distinct thing from a capacity to be sued. The same feudal ideas run through all their jurisprudence, and constantly remind us of the distinction between the Prince and the subject. No such ideas obtain here; at the Revolution, the sovereignty devolved on the people, and they are truly the sovereigns of the country, but they are sovereigns without subjects..."

https://supreme.justia.com/cases/federal/us/2/419/