If the free-range pet is in breach of your by-laws, the easiest option is to invite the irritated EC member to table a motion at your next EC meeting to issue a notice to comply. Your EC doesn’t have to agree – and you might want to speak against the motion or organise the votes beforehand – but at least you have ticked all the necessary boxes.
If the aggrieved EC member wants to take it further, then he or she can raise the issue themselves at Fair Trading which will cost them just this side of $80.
You could even come at it from a different angle and propose an amendment to your pets by-law at your next general meeting, allowing pets to be allowed to run free provided they have prior written permission from the EC, which can be withdrawn if they prove to be a nuisance.