User blog comment:FairyRaven/Fairy Tail Chapter 337: The Golden Plains, Review and Commentary/@comment-60.53.102.237-20130703114213/@comment-60.53.102.237-20130704142329

The reason why the Dragons can came out of the gate is because the presence of a full moon disrupts the Magic Power contained within, resulting in the Gate running rampant making it a "reverse" gate for the Dragons to come through.