Note on the ‘implied undertaking’
The High Court in Hearne v Street  235 CLR 125 confirmed that documents provided by a party to proceedings under compulsion (pursuant to court orders, by way of discovery or other compulsory court processes) are subject to an ‘implied undertaking’ given to the court by the party receiving the documents not to use the documents for any purpose other than litigation. The use of such documents for an ulterior purpose constitutes a breach of the ‘implied undertaking’.
It was held by Hayne, Heydon and Crennan JJ in Hearne v Street (2008) at  that “where one party to litigation is compelled, either by reason of a rule of court, or by reason of a specific order of the court, or otherwise, to disclose documents or information, the party obtaining the disclosure cannot, without the leave of the court, use it for any purpose other than that for which it was given unless it is received into evidence…”
An example of a breach of the ‘implied undertaking’ would be using documents attained from an opponent for some commercial purpose unrelated to the litigation.
The ‘implied undertaking’ does not apply to documents given voluntarily to other parties to the proceedings. Moreover, it is not necessary, in determining whether there was a breach of an implied undertaking, to prove that the party was aware of their obligations or that any misuse of documents would amount to a breach of the implied undertaking.
Consequences for breaching of the ‘implied undertaking’ are serious and include fines and even imprisonment. The ‘implied undertaking’ is generally discharged once the relevant document is tendered or read in open court. Ultimately, the implied undertaking is a substantive obligation imposed and enforced by law, not a voluntary one.