Q. How do I reference legislation in text in Harvard?

The version of Harvard we use is based on the Australian Government Style Manual, so you may wish to confirm with your supervisor or lecturer that they are referring to the same version of Harvard.

For the version we use, you use the short title of Acts and Ordinances in text, putting the title in italics and including the date the first time you use them (for subsequent references, you just capitalise the Act/Ordinance title and don't worry about the italics or year):

According to the Environmental Protection (Impact of Proposals) Act 1974 it must...

then

...as established in the Environmental Protection (Impact of Proposals) Act.

If it's a specific jurisdiction, sneak that into the sentence or put it in brackets after the Act:

In Queensland's Anti-Discrimination Act 1968 ...

or

In the Anti-Discrimination Act 1968 (Qld)...

Commonwealth is abbreviated to (Cwlth) for jurisdiction.

Bills are considered "unpublished', so they aren't italicised. Other than that you follow the same pattern as for Acts.

Case names are italicised, but only the name - you then include the reference details (not in italics) for the first citation in text, but after that you can just use the case name (or a shortened case name if applicable, such as Smith & ors instead of Smith and others), but continue to italicise. Use "at" to refer to a specific page:

Ghamrawi v. The Queen (2017) 269 A Crim R 146 at 152

then

Ghamrawi v. The Queen

If it's a really well known case that has it's own title, include that in the first reference and then just us it from then on:

The State of New South Wales v. The Commonwealth (1915) 20 CLR 54 (the Wheat Case)

then

The Wheat Case...

All of this is listed on pages 224-228 of the Style Manual, if you want to find it in the book.