Note that the monkey’s fist is an illegal knot everywhere in Australia and you can go to jail just for tying one.
This is [k]not true. You'll often find these at wharves in Australia. They can be viewed as an offensive weapon, so an aggravating factor in an assault (which is probably where the misunderstanding comes from), but the knot itself is perfectly legal and used by sailors as the weighted end of a heaving line.
The knot does not appear in the list of prohibited weapons: https://www.legislation.gov.au/Details/C2018Q00081