Is there a time rule or law on exsisting buildings such as a shed before they no longer need a building permit

i built a garden shed in Australia 12 years ago and the council want to take it down because i never got a permit.i'v heard thers a law stating that if a building has been there longer then x numer of years its legal.

Is there a time rule or law on exsisting buildings such as a shed before they no longer need a building permit
from where you heard that there is a law that if building has been there longer than ten years then it becomes legal,you must find out with that source,or just go to the city hall for your your community code department,and ask about your situation and the solution.may be they will ask you to pay for the permit and let it be there.


good luck