Sorry to tell you this but your No Pets bylaw may not stand up if tested.
Per Cathy Sherry’s recent article: https://www.smh.com.au/business/consumer-affairs/even-goldfish-could-be-banned-until-now-20180904-p501oa.html NCAT last week published a decision that a blanket ban on pets was invalid as it breached the new prohibition on bylaws that are harsh, unconscionable or oppressive.
A complex I am involved in currently has a No Pets bylaw in place, which numerous residents ignore, and at the next AGM we intend to put in a well structured but fair bylaw requiring an independent assessment by a vet of the suitability of the breed of cat/dog etc to the unit. This has been based upon other excellent posts on this forum.
Re your specific question about assistance animals. If they have their animal trained and a permit obtained, and an appropriate medical professional signs off on the residents “condition” being aided by the assistance animal, you would be very hard pressed to get the animal removed, regardless of it your No Pets bylaw is valid or not.
Per https://www.olg.nsw.gov.au/public/dogs-and-cats/information-for-the-community/assistance-animals it is not hard to find a disability that a person could claim that would be very hard to disprove.