South Africa have a pretty strict foreign exchange control policy in place. (with good reason, otherwise I think we would be paying for a few more luxury swimming pools in very exotic and expensive locations all over the world....)
If you intend on trading bitcoin, more specifically taking advantage of arbitrage opportunities on international exchanges, you need to be aware of the exchange controls in place in South Africa and plan your trading strategy accordingly.
Whilst not originally intended for "investment purposes", rules have since relaxed and as a resident, natural citizen of the Republic of South Africa, you currently (04/2016) have a R1m (one million Rand) per annum single discretionary allowance if you are over the age of 18. (This is the total amount which you are allowed "export" per calendar year and not to be confused with the amount of profit you are making).
You can invest up to R10 million per calendar year, provided you have the relevant paperwork in place and have the required tax clearance certificate.
On top of this you our able to invest pretty much any amount in foreign investments, provided you have made the necessary applications to the relevant regulatory bodies such as SARB, SARS, FIC.
You can find an in depth look into exchange controls on our blog