"For years now, 'stop and frisk' has been the subject of extensive public filings and intense media scrutiny. Whatever the merit of the unions' claim that Judge Scheindlin's rulings were incorrectly premised 'upon statistical evidence purporting to place 4.4 million stops at issue,' allowing the unions to revive a now settled dispute by intervening at this late juncture would substantially prejudice the existing parties and unduly encroach upon the city's inherent discretion to settle a dispute against it," the ruling said.