By Gabriela Baczynska and Karolina Tagaris BRUSSELS/ATHENS (Reuters) - The European Union said on Monday a Syrian asylum seeker's successful appeal against deportation to Turkey proved the bloc's deal with Ankara to limit migration was legal, while rights groups said the ruling exposed its "fundamental flaws". A Syrian national last week won the second and final appeal to Greece's asylum committee, which ruled the person would not be safe if returned to Turkey under an accord obliging Ankara to take back refugees and migrants who use people-smuggling gangs to reach Greek islands by boat from the nearby Turkish coast.