Hard to call it an "agreement" at that point. I thought one of the fundamental rules of contract law is that it can't be signed under duress.

A sovereign nation is just that, sovereign. What it decides isn't an agreement.

You may not want to obey the posted speed limits or pay something the law demands, but that's not about a contract you sign or don't, it's a decision made by a sovereign nation.

Meta will have the option of not posting links to Australian media. But if it does post that, the law applies, and "agreement" is irrelevant.

Did you seriously believe that governments play fair? :-)