DETROIT (Reuters) - Several labor unions filed a lawsuit in federal court on Monday, saying a Michigan law banning compulsory union membership for private sector employees violates the U.S. Constitution. The right-to-work law, which goes into effect in late March, contains provisions that go "well beyond" the limits of federal law, said Andrew Nickelhoff, an attorney for the Michigan AFL-CIO, one of the unions that filed the lawsuit. ...