This is essentially correct. The "personal use" exemption does apply to controlled substances (90-day supply), but the meds must be FDA-approved for human use and you need a USA prescription to prove personal use. If Customs didn't ask for proof, then you got through, but as Dizzy wrote, the DEA can then pick you up on possession without a USA prescription. BTW, this "exemption" doesn't apply to the importation of shipments of controlled substances. For example, suppose I have an American prescription for BTG Oxandrin 10mg. I get it filled somehow in France (where BTG Oxandrin is a big seller). I return to the USA and declare it. I not only brought back a 90-day supply, but I have a USA prescription to prove legal possession. This is legal. Now, suppose I order the Oxandrin online from a French pharmacy and they ship the Oxandrin to me--same amount. This is ILLEGAL.