about space time perspective...Amakasu can read her mind or just read the future to know what's gonna happen or either the past, so there is that, also Amakasu wasn't even born from humanity, sure he represents endless future possibilities, he is a metaphysical existence, but he wasn't created from humanity, he was a human(i think? not sure about his origin or what he truly is) before becoming a Rosei which means shredding his physical boddy and becoming a living dream (though that shouldn't factor now). Also can't he override her authority with causality manipulation?
Other weakness for her authority being
dragging her out of Imaginary Space and outside of the Moon Cell's influence would also nullify the vast majority of her abilities. as i said BFR her in a dream can work (don't think she is capable of escaping metaphysical places)
Or this one
"Power of the Beginning" a gene from which all other human genes originate. Potnia Therion cannot "undo" this trait, and thus those who are able to analyze Potnia Therion and unlock the Power of the Beginning within themselves can prevent BB's Authority from overtaking them.
So, Amakasu does have some ways to ignore her authority, and i'm pretty sure one of these will allow him to do it.
If she ever does those laws thing, Amakasu can either travel somewhere, or BFR her to dreams and fight her there, create new worlds outside of Alaya, read her mind and make countermeasures, other options. So in the end he can summon.
As i have numerously stated before, he can travel between the past, across universes and stuff like that , and read the past or anywhere from time to know what's gonna happen to him, and thus bring he's army there.
Also BFR takes one week now