The Australian Capital Territory (Self-Government) Act (Act no. 106/1988) marked the commencement of self-government in 1988. With the passage of this Act, the ACT was provided a fully elected legislature, an executive and an independent court system. Prior to 1988 the Australian Federal Government and the Commonwealth Parliament governed the Australian Capital Territory from its beginnings in 1911.
Details on the commencement of the Act 1988 are as follows:
Sections 1 and 2: Royal Assent; Sections 3-6, 8-21, 66-68, 73 and 74: 7 December 1988 (documented in Gazette 1988, No. S374); Section 34 Paragraph 8): 31 January 1989 (see Gazette 1989, No. S39); Section 56 Paragraph 1: repealed before a commencement date was fixed; remainder: 11 May 1989 (see Gazette 1989, No. S164).
The Australian Capital Territory (Self-Government) Act 1988 has had numerous amendments, as listed at http://www.comlaw.gov.au/Series/C2004A03699/Compilations