PARIS - France's Constitutional Council ruled on Tuesday that a new law that would make it illegal to deny the mass killing of Armenians by Ottoman Turks nearly a century ago is unconstitutional, a move likely to help defuse a brewing spat with Turkey.The decision by France's highest legal authority invalidates the law, which President Nicolas Sarkozy was due to ratify by the end of February, ahead of a parliamentary recess for the April-May presidential election.Turkey has threatened to cut all diplomatic relations with France over the legislation, which has been approved by both houses of parliament but had been challenged by lawmakers who appealed to the Council to make a ruling.In a statement, the Council ruled that the law, which would have imposed a 45,000-euro fine, a one-year prison sentence, or both, on genocide deniers, ran against the principles of freedom of expression written into France's founding documents.