Shouldn't they be tracked down whereever they are and tried in court?
You CAN take them to court. But you have to know who they are, and they have to be in a jurisdiction that you are part of. This calls for an Internet private eye. If the country of their jurisdiction is outside of yours, it can be very costly to try them in the other country.
Also, we don't want to invoke International courts any more than necessary. The Internet is about keeping communication freedom free. Getting International courts to mess in Internet freedom does more harm than it does do good.
Also, I believe the CIA and NSA are behind many DDoS attacks. It will be difficult doing anything about them, even if you track back to them as the source of your problem.
The better idea is to set up some kind of DDoS protection ahead of time.