How did the case united states v. e. c. knight weaken the sherman antitrust act? the supreme court ruled that the american sugar company was a legal monopoly since it existed only in one state. the supreme court ruled that the american sugar company was a legal monopoly since it operated in several states. the supreme court ruled in favor of the american sugar company since it controlled only fifty percent of the sugar-refining factories. the supreme court ruled against the american sugar company since it controlled ninety-eight percent of the sugar-refining factories.