Section 51(v) of the Constitution of Australia
Section 51(v) of the Constitution of Australia (commonly referred as the post and telegraph power) is a subsection of Section 51 of the Constitution of Australia that gives the Australian Parliament power to legislate on "postal, telegraphic, telephonic, and other like services". == Postal services == In 1901, one of the first Acts of the federal parliament was the Post and Telegraph Act 1901, relying on Section 51(v).
Source: Wikipedia — Section 51(v) of the Constitution of Australia (CC BY-SA 4.0)