Ayya Tataaloka on the eight "Principles to be Respected" by nuns (garudhammas) and the formation of the female Buddhist Order (bhikkhuni-sangha). The additional monastic rules for women are a "definite historical impossibility." Their origin stories in the Vinaya contradict the famous story of the Buddha's stepmother (the first female to be ordained) and how she was reluctantly granted admission. The venerable nun is at a dialogue seminar in 2008 addressing the topic of the nun's disciplinary code.
A Painful Ambiguity - Ajahn Sujato
The Buddha is said to have laid down eight "Principles to be Respected" (garudhammas) as a prerequisite for female ordination...The eight are like a dam that holds back the floods (buddhanet.net).