The International “law” you’re pointing out is a non-binding agreement to which Australia is a signatory. Note the non-binding part.

The United Nations Declaration of the Rights of Indigenous Peoples is not an "international law". I also alluded to the fact that it was non-binding by stating that Australia was committed to it "in principle". This is not the gotcha you thought it was, try again.

It also didn’t exist when these events took place and retroactively applying laws tends to be a non-starter.

Terra nullius and international law did exist during the period of Australia's colonisation. Are you really this ignorant of history?

Sovereignty as a concept has existed far longer than Colonial powers as I pointed out which you haven’t rebutted in the slightest.

I don't need to rebut it. You clearly described sovereignty under international law in your very first comment. Every attempt you have made to define Australia's sovereignty has been under those terms. Are you suggesting there is more than one form of sovereignty? Didn't you start off by claiming the complete opposite? You've backed yourself into a corner where the only option left is to admit that I am correct. Congratulations on completely playing yourself.