Arrested in Japan for ADHD medication: prescription drugs that are illegal here

You have taken the same medicine for years. A doctor at home prescribed it, the bottle is labelled, and you packed it exactly as you always do. Then an officer at the airport asks you to step aside, and within an hour the conversation is no longer about customs paperwork but about a criminal offence.

This is one of the most common ways in which a law abiding visitor becomes a criminal suspect in Japan. What feels like continuing treatment is treated here as a drug offence. And drug offences sit under a distinctly harsher immigration regime than almost any other crime, which is the part most people learn far too late.

Below: which ingredients trigger which statute, what advance procedure exists, and exactly how a conviction affects your status of residence and any future entry into Japan.

Japanese law looks at the active ingredient, not the brand

The decisive question is not what the box says but what is inside it. Medicines whose active ingredient is amphetamine or methamphetamine may fall under the Stimulants Control Act, which is the statute Japan applies to its most tightly restricted substances. Medicines containing methylphenidate fall under the Narcotics and Psychotropics Control Act.

Both categories are heavily restricted for possession and importation inside Japan even when the medicine is an ordinary prescription item in your own country. A foreign prescription is evidence of medical need; it is not a Japanese permission. Because products sold under similar names can contain different ingredients from country to country, the check has to be done at the level of the ingredient, in writing, before you fly.

There is an advance procedure for bringing medicine in

Japan does not simply tell patients to go without their treatment. For medicines classified as narcotics or psychotropics, there is a system under which a traveller who needs the medicine for their own treatment applies in advance to the competent administrative authority and obtains permission before entering the country.

In practice the application is supported by a certificate from the prescribing doctor and a written statement of the drug name, the quantity and the period of use, and it takes time to process. Realising the problem the night before departure is usually too late. Where the active ingredient falls under the stimulants category, carrying the medicine in may not be permitted at all. That is not a judgement call to make on your own at the airport; it is a question to settle in advance with the authority.

Why a drug case is different from every other criminal case

Here is the point that matters most. Article 24, item 4 (chi) of the Immigration Control and Refugee Recognition Act makes a person subject to deportation if they have been found guilty of violating laws concerning narcotics, cannabis, opium, stimulants and similar substances. A fine is enough. A suspended sentence is enough. Even an exemption from punishment is enough. It does not matter whether your status of residence appears in Appended Table 1 or Table 2.

Compare this with article 24, item 4 (ri), which covers a person sentenced to life imprisonment or to kōkinkei (拘禁刑, the unified custodial penalty under current Japanese law) exceeding one year, and which contains a proviso excluding those whose sentence is fully suspended. Item (ri) opens with the words in addition to those listed in (ni) through (chi), which is precisely why drug cases are handled outside its framework and outside the protection of its proviso.

The second difference concerns re entry. Article 5, paragraph 1, item 5 of the same Act sets out landing refusal for drug related violations with no time limit attached. A fine is sufficient, and a conviction under a foreign law can also be sufficient. Once this provision applies, there is no period after which the bar simply expires. Re entry becomes possible only through special permission to land under article 12, paragraph 1. This is structurally different from the landing refusal periods of one, five or ten years that article 5, paragraph 1, item 9 attaches to a previous deportation.

A third difference is procedural. Departure order under article 24-3 requires, among other things, that the person does not fall under any of items (ha) through (yo) of item 4. A person caught by the drug provision therefore cannot use the departure order route at all. On the other hand, item 4 (chi) is not among the categories listed in the proviso to article 50, paragraph 1, so the route of applying for special permission to stay is not closed. What matters there is building the case around the factors set out in article 50, paragraph 5: the reason for wishing to remain, family relationships, conduct, the circumstances in which the person came to reside in Japan, the length of residence and other circumstances.

Four assumptions that cause real damage

The first is that a doctor’s prescription makes possession lawful. Japanese law does not automatically treat possession based on a foreign prescription as lawful.

The second is that a small personal quantity will be overlooked. Quantity can matter to sentencing; it does not by itself decide whether an offence exists.

The third is that a fine has no immigration consequence. As set out above, in drug cases a fine alone already engages article 24, item 4 (chi).

The fourth is that all controlled substances work the same way. Designated substances regulated under the Pharmaceuticals and Medical Devices Act, for example, are not among the offences listed in article 24, item 4 (chi). Because the applicable statute changes the outcome, identifying the exact ingredient and the exact governing law is not a technicality.

What to do if you are stopped or arrested

Article 198, paragraph 2 of the Code of Criminal Procedure requires that you be told you may refuse to make a statement. If the written record does not match what you said, paragraph 4 of the same article allows you to request that the record be added to, reduced or altered. If you are not comfortable being questioned in Japanese, articles 175 and 178 of the same Code govern the appointment of interpreters and translators. Article 14, paragraph 3 (a) and (f) of the International Covenant on Civil and Political Rights guarantees that you be informed of the charge in a language you understand and receive the free assistance of an interpreter, and article 36 of the Vienna Convention on Consular Relations covers notification of, and access to, your consulate. Your right to meet a defence lawyer rests on article 39, paragraph 1 of the Code.

Practically, gather the prescription, the diagnosis, any medication information sheet, your treatment history, and records of how the medicine was handled on previous trips. As a point of reference, the White Paper on Crime records a suspension of prosecution rate of 15.9 per cent for narcotics cases in 2024. How concretely the therapeutic purpose can be documented is one of the things that can influence the prosecutor’s decision.

How our office works on these cases

Attorney Matsumura Daisuke personally attends detention visits and meetings. For Chinese, the office has a dedicated interpreter for foreign national criminal cases on site; for other languages, including English, an interpreter is arranged according to the individual case.

Our starting position is that a suspended sentence is not a good enough outcome, so obtaining a decision not to prosecute is the priority objective. In drug cases that objective carries particular weight, because it is the guilty finding itself, and not the severity of the sentence, that engages article 24, item 4 (chi). We design the criminal case and the immigration procedure as a single piece of work, and we are prepared to contest intent and negligence at the stage of deportation grounds as well. The first consultation is free, and you can also reach us through WeChat ID matsumura1119.

Closing note

It is genuinely hard to accept that medicine prescribed for a diagnosed condition can become a criminal file. Yet in the Japanese system the ingredient and the paperwork decide almost everything, and both can be checked before you board. This article is general guidance only; for your own situation, please speak to a lawyer directly.

Author

Matsumura Daisuke／Attorney at law
Member of the Daiichi Tokyo Bar Association (registration number: 59077／admitted 2019)
Funado International Law Office (Fuse Building Honkan 3F, Takada 3-4-10, Toshima-ku, Tokyo)
Principal practice areas are criminal defence for foreign nationals and immigration procedures, with clients mainly of Chinese nationality. Results obtained include an acquittal in a Stimulants Control Act case (possession for the purpose of profit), a decision not to prosecute in an organised fraud case, and special permission to stay in a case regarded as difficult.

Funado International Law Office
Website: https://matsumura-lawoffice.jp/
WeChat ID: matsumura1119

Japanese version of this article: https://matsumura-lawoffice.jp/blog/detail/2026099150/