Where in the Controlled Drugs and Substances Act does it talk about trafficking?

You will not find a specific amount. The government must establish the charge of "Possession with intent to distribute". Some is common sense, if you have 2 pounds of cocaine concealed on your body, the government should prove their case. You could also be observed selling Marijuana by the joint, or selling to an undercover agent, and only have a couple left when arrested, but be arrested for distribution. Distribution in most cases is an enhancement of the possession charge. So it is really more about cirstance than quantity. Hope I helped some.