The Supreme Court shall consist of seven justices. The General Assembly may, if three-fifths of the elected membership of each house so vote at two successive regular sessions, increase or decrease the number of justices of the Court, provided that the Court shall consist of no fewer than seven and no more than eleven justices. The Court may sit and render final judgment en banc or in divisions as may be prescribed by law. No decision shall become the judgment of the Court, however, except on the concurrence of at least three justices, and no law shall be declared unconstitutional under either this Constitution or the Constitution of the United States except on the concurrence of at least a majority of all justices of the Supreme Court.