It can be against the law for an employer to not employ someone or offer them less employment opportunities because of their immigrant status.
This does not mean that that an employer has to employ someone who does not have a valid work visa. Australian businesses are only permitted to employ ‘legal workers’ who are entitled to work in Australia. Legal workers are Australian or New Zealand citizens, permanent residents and people in Australia with a valid visa that allows them to work.
Acts of discrimination based on nationality or citizenship are not prohibited by law.