Your protection is your knowledge. Know that you are allowed to cultivate marijuana in private for private use without intention to distribute.
You can reasonably argue personal use at roughly two plants per person within a household. This is not law, it is not written down or referred to anywhere in legislation. Two plants per person in a household is just a legal argument one can use once put to the case in court (if you get taken that far). This is somewhat the case in Australia. South African law does take into consideration laws in foreign nations when precedent is being set (especially now in SA while we still wait for the official legislation).
Let me emphasize that the law is still yet to be written on private marijuana cultivation. Each situation will be argued on a case to case basis. In other words, the less you look like you're dealing and the more you look like it's for personal use, the better off you will be.
Unfortunately then in the case of growing large quantities for yourself, that's the risk my china that is the game you play, and play it well you must.