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.