Although Japan’s immigration exclusion for drug offenders is strict, the US has similar restrictions, and any alien who has committed an offense more serious than possession of ≤ 30 grams of marijuana should NOT expect an easy time of getting into the USA. A waiver is available for very, very limited cases. We cannot be very encouraging to ANYone who has a prior drug conviction or admission.
Those who have been “cautioned” for marijuana possession in certain countries such as the UK and Australia should know that such “cautions” typically include the perpetrator’s admission of the underlying facts of the incident (e.g., the possession). Therefore, the perpetrator has admitted to having committed the violation, even if there was never a trial, a conviction, or other citation. –jcf