What is the effect of the Attorney General's practice of employing special counsel to assist district attorneys in the prosecution of civil cases?

"It has been the practice of the Attorney-General for many years to employ special counsel to assist district attorneys in the prosecution of suits pending in their respective districts whenever the public interest demanded it. It has been the practice of such special counsel to appear, with the district attorney, before grand juries and committing magistrates and to assist in the proceeding pending there. This right passed unchallenged for many years, until the circuit court for the southern district of New York, on March 17, 1903, (decided) the case of the United States v. Rosenthal. . . .