This is the official site for Australian Commonwealth legislation, and contains the most up to date full text of all relevant Acts.
It also contains:
Historical versions of current legislation for approximately the last 30 years, including amendment information.
Older versions of legislation that is no longer in force.
Here is a list of Commonwealth Acts relating to migration and citizenship:
These can be also be found in the Federal Register of Legislation. Note that in this database, Regulations are also referred to as Legislative Instruments.
Here is a list of Commonwealth Regulations relating to migration and citizenship:
These databases all have special features that allow you to find relevant cases and other associated materials.