Wrong. Seriously, some people need to learn some facts before running their mouths off with hunch feelings sprouted as facts. Might get you into a bit of hot water down the track.
Macquarie University Law Society gives free membership to all law students. It doesn't cater ANYTHING for non-law students and the only thing non-law students might do is attend the law harbour cruise and possibly the law ball (though both those events are organised by the society and aimed primarily at law students).
There aren't any MAJOR differences between law socs of the different unis in regards to be 'exclusiveness' or whateva, except some might not give free memberships to law students.