THC Liquid, Cannabis Gummies and CBD Products: Laboratory Analysis and How to Argue "I Didn't Know"

A product bought legally overseas. Something ordered online or picked up in a shop in Japan. A souvenir handed to you on a trip. Every so often, a regulated substance is detected in items like these and the owner finds themselves under investigation without ever expecting it. The appearance of a product and its brand name often reveal nothing about which legal category it falls into. For a foreign national, how that question is answered reaches beyond criminal liability and into the future of your status of residence (在留資格). This article sets out the issues surrounding laboratory analysis and how to present what you understood at the time of purchase.

Key points

• Since 12 December 2024, cannabis has been regulated as a narcotic under the Narcotics and Psychotropics Control Act (麻薬及び向精神薬取締法).
• Which substances a product contained is established only by laboratory analysis. The product name and what the seller said do not settle it.
• If the substance is found to be a narcotic under that Act and a guilty verdict follows, a ground for deportation (退去強制) arises under Article 24, item 4(chi) of the Immigration Control and Refugee Recognition Act (入管法).
• Whether you had the necessary intent or knowledge is a criminal issue, and it is also the foundation of the arguments you will make in the immigration procedure that follows.
• Article 5, paragraph 1, item 6 of the Immigration Act makes a person who unlawfully possesses narcotics, cannabis, stimulants or comparable substances subject to denial of landing (上陸拒否).

If the product was legal where I bought it, does that protect me in Japan?

It does not. What is regulated inside Japan is determined by Japanese law. As a matter of principle, the fact that a product was lawful in the country of purchase has no bearing on whether the elements of a Japanese offence are made out.

As for cannabis, since 12 December 2024 it has been regulated as a "narcotic" under the Narcotics and Psychotropics Control Act. Possession, transfer and acquisition carry imprisonment (拘禁刑) of up to seven years under Article 66, paragraph 1, rising where there is a profit-making purpose to imprisonment of between one and ten years under paragraph 2, with a fine of up to 3 million yen imposed in addition depending on the circumstances. Use and receiving administration carry imprisonment of up to seven years under Article 66-2, paragraph 1. Importing, exporting and manufacturing carry imprisonment of between one and ten years under Article 65, paragraph 1, item 1.

Bringing a product bought abroad into Japan may therefore be treated as importation, depending on what it contains. Cases regularly come to light through baggage inspection at airports or through the examination of international mail.

Laboratory analysis is the starting point

The law that applies is determined by the composition of the seized item. This is the first thing to establish.

With products in liquid, food or cosmetic form, nothing about the outward appearance reveals what is inside. If a regulated substance is detected, the case falls under the Narcotics and Psychotropics Control Act; if the substance goes no further than a designated substance (指定薬物), the case falls under the Pharmaceuticals and Medical Devices Act (医薬品医療機器等法). The two carry different consequences for your residence, which makes the distinction decisive.

As for the analysis itself, there are numerous points to verify: whether the material analysed is identical to the item seized, how the item was stored between seizure and analysis, the method used, and what the detected figures actually mean. This calls for requesting disclosure during the investigation and, where appropriate, obtaining expert input as the review proceeds.

How do you build an argument that you did not know what was in the product?

By assembling objective circumstances, one on top of another. Knowledge is a state of mind, and it cannot be established by the client's own account alone.

The following are among the matters that give the argument something to work with.

The task is to gather these carefully and present the sequence from purchase to possession as a single coherent account. Statements given during questioning can shift in nuance as they pass through an interpreter, so checking what the written record actually says is indispensable.

• How the product was obtained, and what labelling or explanation the seller provided at the time
• Whether the price paid makes sense for a transaction in a regulated substance
• How the product was stored, whether it was shared with others, and whether there was any attempt at concealment
• The purpose of use and the specific sequence of events leading to the purchase
• Objective material such as messages, purchase histories and receipts that corroborates what you understood at the time

Contesting intent also feeds into the immigration procedure

Disputing knowledge at the criminal stage, and preserving a record of how that dispute unfolded, has value for the procedures that come afterwards.

Immigration practice has for many years followed the position that intent and negligence are not elements in deciding whether a ground for deportation exists. Attorney Daisuke Matsumura is currently litigating a case, arising from a deportation based on the facilitation of unlawful employment, that squarely asks whether the principle of individual culpability should extend to deportation as an administrative disposition. We cannot anticipate the outcome, but it is a live issue.

Cases turning on what a person knew about the contents of a product are exactly where that issue takes on real weight. Contesting knowledge thoroughly in the criminal process, and preserving both the argument and the supporting evidence, lays the foundation for what can be said later in the deportation procedure and in an application for special permission to stay (在留特別許可). Conversely, making an easy admission in order to secure early release is difficult to undo in later proceedings.

What happens if you are convicted

A guilty verdict for an offence under the Narcotics and Psychotropics Control Act gives rise to a ground for deportation under Article 24, item 4(chi) of the Immigration Act. That item refers only to a person who "has been found guilty", with no limit as to type or length of sentence and no exception for a suspended sentence.

Article 5, paragraph 1, item 5 of the Immigration Act, in turn, makes a person who has been sentenced for violating legislation controlling narcotics, cannabis, opium, stimulants or psychotropic substances subject to denial of landing, and no time limit is attached to it. Item 6 of the same paragraph makes the unlawful possession of these substances a ground for denial of landing in its own right. For someone who came to Japan as a tourist or on a short visit, this means re-entry may be closed off for a very long time.

This is why, in drug cases involving foreign nationals, a strategy aimed at securing a suspended sentence at trial is not enough. The defence has to be built around obtaining a decision not to prosecute (不起訴処分) before charges are brought.

How our office works

At Funado International Law Office (3F Fuse Building Main Wing, 3-4-10 Takada, Toshima-ku, Tokyo), attorney Daisuke Matsumura personally handles every stage, from the first detention-centre visit through to the close of trial. As a matter of policy, we do not delegate the work to clerical staff or junior lawyers.

For Chinese, a dedicated interpreter experienced in cases involving foreign nationals is on staff. Separate from the interpreter appointed by the investigating authorities, you can use an interpreter who acts for you throughout the criminal process. For English, Vietnamese, Korean and other languages, we arrange an interpreter to suit the particular case.

From cases we have handled

In one case, a client prosecuted under the Stimulants Control Act (覚醒剤取締法) for possession with intent to profit was acquitted following exhaustive analysis of the evidence and careful examination of the defendant and cross-examination of witnesses (A-1). Where knowledge is the central issue, the outcome turns on testing every objective circumstance one by one.

In another, we acted for a woman wrongly accused of facilitating unlawful employment who faced deportation, and we are currently litigating a case that asks how far the principles of individual culpability and fault-based liability extend (D-2). In that same matter we obtained special permission to stay in a case where facilitation of unlawful employment had been found, an outcome with no prior example.

We have also handled international criminal cases, cases tried before lay judge panels, and serious matters reported worldwide (E-1).

A product's name and the seller's description do not determine its legal classification. Establish first how the substance has been identified, then set out the sequence from purchase to possession with objective material to support it. Following that order is, in our view, the surest way forward for both the criminal case and your residence. This article is a general explanation. For your own situation, please consult a lawyer directly. The past results described above turned on the particular circumstances of those cases and are not a guarantee that a similar outcome will be achieved.

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