Here I wish to briefly add to the earlier discussion on the validity of bhikkhunī ordination by bhikkhus only.
One of the main bones of contention between Venerable Analāyo (VA) and Ajahn Ṭhānissaro (AT) is whether the Vinaya narrative, also known as the origin stories, can be used in the interpretation of the rules. VA has relied on the narrative to make sense of the Khandhaka rules on the ordination of bhikkhunīs, whereas AT has argued quite forcefully that this is inappropriate. To try to find a resolution to this, I have recently written a short paper on this issue as part of a longer paper co-authored with VA. The conclusion of the paper is that not only is it permissible to use the origin stories to interpret the Khandhaka rules, it is absolutely necessary. The rules can in fact not be understood without the narrative framework.
The actual paper can be read here: VinayaComy, final, as published.pdf (177.1 KB).