The relevant legislation is the Animal and Plant Control (Agricultural Protection and Other Purposes) Act 1986. The Act is administered by the Animal and Plant Control Commission (APCC), with local Animal and Plant Control Boards responsible for implementing the Act within the local government incorporated areas of the State. The Commission administers the Act in those areas of the State not within a local Animal and Plant Control Board area. The APCC is part of the Department of Water, Land and Biodiversity Conservation and weeds prohibited by legislation in SA are listed on their website at http://www.dwlbc.sa.gov.au/biodiversity/pests/apcc.html
There is a consolidated proclaimed pest plants list; including a summary list. Please note that it is the prohibited plants listed in subsection 54(2) that apply to persons or companies selling seed in South Australia. This section [54(2)] prohibits the sale of produce contaminated with any of the listed plants. As this subsection covers all types of produce (fodder, livestock, soil etc) not all of the plants listed are seed contaminants. Some (for example; bulbil Watsonia, salvinia, horsetails) have no seeds.
The list of weeds prohibited by legislation is not necessarily the same as the list of weeds prohibited in Seed Services Australia's (SSA) Seed Certification Scheme. The prohibited weed list for the SSA Seed Certification Scheme is published as Appendix 10.2 of the Procedures and Standards of the SA Seed Certification Scheme Manual (May 2002). Please note that there is no longer a Declared weed seed category in either legislation or the certification scheme. Scheme rules will be updated to reflect this change.
Weeds Australia website www.weeds.org.au includes a comprehensive Summary of State & Territory Noxious Weeds Legislation.