Citing their free speech rights, three tour guides in Philadelphia filed a lawsuit this week challenging an ordinance that will require them to pass a history test and get a license. Mayor Michael Nutter signed the measure into law in April amid concern that some guides were perpetuating gross inaccuracies, including the false claims that Benjamin Franklin had 69 illegitimate children and that Betsy Ross, a three-time widow, killed her husbands. But the three guides, Ann Boulais, Michael Tait and Josh Silver, backed by a public-interest law firm, argue that the city has gone too far. The tests will be required beginning in October. Washington, New Orleans and Charleston, S.C., have similar ordinances regulating tour guides.