Otis was a fervent opponent of the writs of assistance imposed by Great Britain on the American colonies in the early 1700s which allowed law enforcement officials to search private property without cause.

Their elder daughter Elizabeth was a Loyalist like her mother; she married Captain Brown of the British Army and lived in England for the rest of her life.

[11][12][13][14] Otis considered himself a loyal subject to the Crown, yet he argued against the writs of assistance in a nearly five-hour oration before a select audience in the State House in February 1761.

[16] John Adams recollected years later: "Otis was a flame of fire; with a promptitude of classical allusions, a depth of research, a rapid summary of historical events and dates, a profusion of legal authorities.

"[17] Adams promoted Otis as a major player in the coming of the Revolution, writing nearly 50 years later: "Then and there was the first scene of the first Act of opposition to the Arbitrary claims of Great Britain.

Otis was the first leader of the period to develop distinctive American theories of constitutionalism and representation, but he relied on traditional views of Parliamentary authority.

He refused to follow the logical direction of his natural law theory by drawing back from radicalism, according to Ferguson, who feels that Otis appears inconsistent.

[23] According to Matthew K. Reising, Otis developed his argument regarding Parliamentary authority by examining the effects of the Glorious Revolution in America rather than the historical situation of 17th century Britain.

Otis, at times, counseled against the mob violence of the radicals and argued against Adams's proposal for a convention of all the colonies resembling that of the Glorious Revolution of 1688.

The idea of racial equality also permeates his Rights of the British Colonies (1764), in which he states:The colonists are by the law of nature freeborn, as indeed all men are, white or black.Otis suffered from increasingly erratic behavior as the 1760s progressed.

Thomas Hutchinson wrote to Governor Bernard in December 1771 that "Otis was carried off today in a postchaise, bound hand and foot.

Massachusetts Governor John Hancock held a dinner in his honor in 1783, but the event was too much for Otis's fragile mental state and he returned to the countryside.