There's plenty of laws and legislation put forth by various bodies that an agriculturalist must adhere to. They cover such things as bio-security, environmental hazards, safe working procedures, animal rights and what can or cannot be farmed.
Most of it is all standard stuff that you would already guess due to it's obvious nature, let's take gun laws for example, your gun must be locked up when not in use and it must be registered. That's fair enough.
There's other legislations that are there to protect properties, avoid disputes and protect the public. Consider the laws relating fencing. They must be up to standard and maintained to protect travelling motorists from stray animals.
Fuel, chemicals and fertilisers are to be correctly used, disposed of and stored along with relevant SOPS and MSDS's. We can't be in a situation where chemicals are allowed to contaminate the environment nor become a threat to workers on the farm or poison food earmarked for consumption.
Your vehicles must be roadworthy and registered, again fair enough. You can purchase a partial registration for vehicles that only do a small amount of travel by the way. Also, tractors must have a roll bar if they don't have a cab.
Be aware of children on the farm, remember they can't read warning signs or chemical labels for example so Safework SA has some great guidelines that will keep the little ones safe.
Bushfire regulations are a big one. I made contact with the CFS who directed me to a range of resources on their website. In particular I was interested in regulations regarding on farm fire units for which the CFS has created a handbook. Some of the basics here are in respect to ensuring the unit is correctly and safely attached to the vehicle. If you consider the weight of the tank full of water and the dangers if the tank isn't properly restrained. I also asked what requirements were in place for setting up your property to make it more fire safe and in this respect I was directed to council regulations as this is the councils domain. So things like burn offs and wind breaks are not regulated by the CFS but each council area.
The RSPCA deals with a range of standards that must be adhered to. Assessors will come to the farm to ensure standards are being met. They range from such things as adequate shelter, food and water, stocking levels and that handlers are correctly trained.
The main thing to be aware of is that there are a large range of bodies and associations that set standards as well as the government. It is important to take the time to be aware of them all for the better of your farm and the industry.