Board Thread:General Discussion/@comment-24815992-20140516131902/@comment-24384892-20140518180115

I don't think it's Yammy's rank in his released form that matters. It's his rank in his base form that does. Because Yammy is only #10 in his base form, technically he doesn't count as one of the top 4 Espada.

Besides, even if this does count as breaking a rule, Grimmjow has also broken one. It is forbidden for the Espada to use Gran Rey Cero inside of Las Noches, but Grimmjow used it in his fight against Ichigo.