Treaties have the force of law, which is why they're such important documents. Your local law does not apply to materials originating outside of that jurisdiction.
You seem very knowledgeable, so let me only add what I know to be true: this is location and context dependent.
For example: If I make a contract with another Australian (company, individual, whatever), no treaty has an effect on that contract unless legislation has been passed to enact that treaty. A judge may refer to the treaty if there is some ambiguity that requires his/her discretion, but the treaty itself is not legally binding.
Quite. But if you make a contract with me (in the US) you wouldn't be able to blow it off under cover of Australian law, is what I mean. So if Elsevier's contract terms are legal in their (Elsevier's) domicile, people who enter into contracts with them need to keep that in mind - which is why most contracts have a 'choice of law' provision saying which laws will govern the enforcability of the contract in the event of a subsequent dispute.
For example: If I make a contract with another Australian (company, individual, whatever), no treaty has an effect on that contract unless legislation has been passed to enact that treaty. A judge may refer to the treaty if there is some ambiguity that requires his/her discretion, but the treaty itself is not legally binding.