During the period required to establish WA residency for admission to the Western Australian bar he travelled over the colony particularly to the eastern mining areas, at that time in the rise of a major gold boom.

[5] At the general elections for the Western Australian Legislative Assembly in 1897, Pennefather stood for the Greenough constituency as a supporter of the Forrest Government, winning the seat by a substantial majority.

In October 1897 Premier Sir John Forrest appointed Pennefather Attorney-General in the Cabinet upon the retirement of Septimus Burt.

[5] In 1901 Pennefather resigned his Legislative Assembly seat, was appointed KC and Acting-Justice of the WA Supreme Court, during the leave of absence of the Chief Justice.

[7] He died there on 16 Jan 1914 after a long illness, hastened by a Perth summer heat wave, survived by his wife and daughter.