Could I Be Prosecuted at Home for a Drug Case in Japan? How to Think About the Double Risk

Once the shape of the Japanese proceedings finally becomes clear, a new worry tends to surface: what happens after going home. Will the fact of being dealt with in Japan cause problems in the home country? Could there be another investigation there? Many people carry that question around for months. To be honest at the outset, there is no single answer we can give. Legal systems and practice differ from country to country, and we are not in a position to state definitively what the law of your country provides. What this article does, while avoiding assertions we cannot support, is show you what to ask, whom to ask, and how.

Key points

• Whether you can also be punished at home depends on the country, and it is not something a Japanese lawyer can answer across the board.
• Some countries have provisions allowing them to punish acts committed outside their territory.
• How far the principle against being punished twice for the same act extends across borders also varies from one legal system to another.
• Effects on residence status, professional qualifications and passports in the home country also differ by country. Checking with a lawyer in your own country is the reliable route.
• The Japanese consequences, by contrast, are clear on the face of the statute. Given the effect of Article 24(4)(chi) and Article 5(1)(v) of the Immigration Control and Refugee Recognition Act (入管法), concentrating on the Japanese proceedings is the realistic course.

If I am dealt with in Japan, will I also be punished at home?

There is no across-the-board answer. That is not lawyerly caution; it is simply the position. The reach of a country's criminal law, how it treats acts committed abroad, and what weight it gives to a foreign punishment are all matters determined by each country's own legislation, and they differ widely.

There is plenty of material online stating confident conclusions about particular countries. But amendments and changes in practice are common, and the answer may turn on your nationality, on what exactly was done, and on the type of disposition reached in Japan. On Japanese law we will explain clearly, on the basis of the provisions. On foreign law, our policy is not to answer by guesswork.

The idea of punishing acts committed abroad

The criminal law of many countries starts from the principle of punishing acts committed within its own territory, while providing that in certain cases acts committed abroad may also be punished. Provisions covering acts committed abroad by a country's own nationals are one familiar pattern; provisions covering particular serious offences committed abroad are another.

How far the principle against being punished twice for the same act extends beyond national borders is also viewed differently from country to country. How a foreign final judgment is treated in domestic proceedings, and whether time served abroad is credited, are questions that cannot be resolved without checking that country's law. It is safer, therefore, not to assume that the outcome in Japan automatically settles the position at home.

How does information reach my home country?

What information reaches the authorities of the home country, and by what route, is likewise something we cannot answer in general terms, since it depends on the content of arrangements between states and on each country's own practice. Here too, explanations based on speculation are best avoided.

What can be said is that where a foreign national is arrested, notification of the consular post of the home country can be requested under Article 36(1)(b) of the Vienna Convention on Consular Relations. This exists so that a person deprived of liberty can receive the protection of their own state. Whether to request notification is something to consider after confirming the wishes of the person concerned.

What to ask a lawyer in your own country

Setting out your questions in advance lets you cover the essentials even in a short consultation. Conveying the Japanese disposition accurately is the starting point, so keep the documents recording it safe, and prepare a translation where necessary.

• Whether your country's criminal law contains provisions punishing drug-related acts committed abroad
• How a foreign conviction, or a foreign decision not to prosecute, is treated in your country's procedures
• Whether there may be restrictions on issuing or renewing a passport, or on leaving the country, after your return
• Whether professional licences, qualifications or official registrations may be affected
• Whether there is any change to residence, civil registration or social security entitlements at home

Why we still ask you to concentrate on the Japanese proceedings

While the position at home is uncertain, the Japanese consequences are fixed in the text of the statute. Article 24(4)(chi) makes a ground for deportation of anyone convicted of violating the Narcotics and Psychotropics Control Act, the Act on Regulation of Cannabis Cultivation, the Opium Act, the Stimulants Control Act, the Anti-Drug Special Provisions Act, or Chapter XIV of Part II of the Penal Code, with no limitation as to the type of penalty or its length. Article 5(1)(v) then makes a person who has been sentenced for violating drug control laws subject to denial of landing (上陸拒否), with no time period attached.

What these two provisions mean together is plain. Without a conviction in Japan, neither of them operates. So in a foreign national's drug case, the objective is not a suspended sentence at trial but a decision not to prosecute (不起訴処分) before charges are laid, which is the complete way out that protects residence. Concentrating your energy where it can still make a difference will do more good than worrying about an uncertain future.

How our office works

At Funado International Law Office, attorney Daisuke Matsumura handles every stage personally, from the first detention visit through to the close of trial. In cases with an international element, the fine detail of the client's account frequently decides the outcome. For Chinese, we have a dedicated interpreter on staff who is experienced in cases involving foreign nationals, so that, separately from any interpreter appointed by the investigating authorities, you have the use throughout the criminal process of an interpreter working for you. For languages other than Chinese, including English, we arrange an interpreter to suit the case.

Renewals and changes of status of residence (在留資格) after the criminal process ends are handled on a one-stop basis together with an administrative scrivener we work with. On questions about the legal system of your own country we cannot give a definitive answer, but we can help you organise the points that need to be checked.

Matters we have handled that may be of reference

Our office has acted in international criminal matters, in lay judge cases, and in serious cases reported internationally. Where a case crosses borders, the evidence and the people involved are spread across several countries, and reconstructing what actually happened can itself be difficult.

We obtained an acquittal for a client prosecuted for violating the Stimulants Control Act (possession for the purpose of profit), through thorough analysis of the evidence and through examination of the defendant and cross-examination of witnesses. For a client who had lost their status of residence and was arrested and prosecuted for overstaying, working in difficult conditions in which almost no official documents from the country of nationality existed, we gathered favourable evidence and analysed the immigration authorities' previously published grants, obtaining special permission to stay (在留特別許可) on a single application. Past matters turned on their own particular facts, and no similar outcome can be promised.

Worrying about what happens after you return home is entirely natural. But much of that worry takes a clearer shape once the questions are actually put. On your own country's system, ask a lawyer there; on the Japanese system, ask a lawyer here. Divide the work that way and the picture gradually comes into focus. This article is a general explanation; for your own situation, please consult a lawyer directly. Past matters turned on their own particular facts, and no similar outcome can be promised.

This article reflects the law as at August 2026.

About the author

Daisuke Matsumura, Attorney at Law
Dai-Ichi Tokyo Bar Association (registration no. 59077, admitted 2019)
Funado International Law Office (Fuse Building Main Wing 3F, 3-4-10 Takada, Toshima-ku, Tokyo)
Practice focused on criminal defence for foreign nationals and immigration proceedings.
Results include an acquittal in a Stimulants Control Act case (possession for the purpose of profit), non-prosecution in organised fraud cases, and special permission to stay in cases regarded as difficult.

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