A sutra or a rule is said to be asiddha in regard to another if, with respect to this latter, it is conceived of as not to exist.
Sutra 6.4.22 which reads - असिद्धवदत्रभात् | (asiddhavadatrabhaat) is an adhikara sutra that defines the limits up to which it is valid as अभात् (a bhaat), in which sutra the word अत्र (atra) means - in that domain or in the domain of the same conditioning element.