Indigenous Australians, like all vulnerable persons, are highly disadvantaged by the complex nature of legal language – keeping in mind that legal language is itself a dialect of English. This disadvantage extends to written language, and written contracts can be particularly complex. 
I have attached a podcast entitled Contracts in Comic Form,  within which is discussed the new legal concept of legal contracts in comic and pictorial form. This type of contract is highly likely to be held to be legally binding and will be of great value to vulnerable parties such as Indigenous Australians, and consequently reduce the differential in power that exists between contracting parties (particularly) when one of those parties is vulnerable.
It strikes me this is a field of inquiry that would be worthy of study for any linguist hoping to make an impact upon the substantive disadvantage experienced by Indigenous Australians with regard to the Australian legal system.
 An excellent example of complex legal language is the contract that was the
subject of Karam v ANZ Banking Group Limited & Ors  NSWSC 709. This contract
was examined in detail by Tanner (2000), who focused upon a single paragraph (‘the
sentence’) which consisted of a single sentence of 80 single spaced lines, 1688 words,
53 clauses, and 54 reduced clauses. The sentence contained the “word ‘or’ 153 times”
meaning the sentence could be written in 9.6 x 10^35 different ways (Tanner 2000, p. 62). In fact the sentence was so complex that ANZ’s own Counsel was unable to interpret
 Australian Broadcasting Corporation, Radio National. (2016). Comic Contracts. Retrieved 17 October 2016, from http://www.abc.net.au/radionational/programs/lawreport/comic-contracts/7898330
 Tanner, Edwin. 2000. “The Comprehensibility of Legal Language: Is Plain English the
Solution?” Griffith Law Review. 9 (1)