In the aftermath of the Snow Queen's spell, portals were opened up all over Storybrooke bringing in people from realms far and wide - across all universes (even the alternate ones). In a desperate attempt to protect the world at large from the influx of these newcomers, Regina sealed off Storybrooke permanently, making it impossible for anyone to leave the magical town.
Thank you both for coming to see Alexia the other day. She recognized your faces right away and was so happy to see you both. I hope you'll consider coming to see her in the future.