If it is done already then you have probably lost the old rules and would need (I believe) a special resolution to get them back. However, since they were existing rules, it might be easier to get them back as it could be presented as intended to reinstate what had been the status quo while still also having the new default rule set, which does not sound unreasonable. Perhaps easier than trying to bring an entirely new set of rules.
However, on the pets example, in the ACT at least, a blanket ‘no pets’ rule would be almost impossible to have since it would be almost always incompatible with a provision of the Act which says that an owners must seek permission to have a pet but it must not be unreasonably refused. As a consequence, we have rules that gives automatic permission to certain numbers of certain sorts of animals but requires explicit individual permission for any other sorts. We require any animal to under the control and supervision of a responsible person when it is on the common property but we don’t ban them from the common property. This has the effect of requiring cats to be contained just like any other animal. This was the most contentious feature and very much welcomed by some but strongly opposed by a few. Nonetheless we got our rule passed with grandfathering of the relatively small number of cats that were accustomed to roaming.