The functions and authority of a JP are set out in section 8 of the Justices of the
Peace Act 2002, which gives JPs the authority to exercise functions conferred by
or under the Act, the Oaths Act 1900 (NSW) (especially sections 21 and 26), or any
other NSW Act. These are the only functions that you can exercise when you are
acting in your capacity as a JP.
You must be physically present in NSW to exercise your functions as a JP,
including to witness any statutory declaration or affidavit. You are not authorised
to exercise JP functions while you are in any other state or territory (including the
ACT) or another country.

www.jp.nsw.gov.au/Documents/Section-4-JP-handbook.pdf