The Grammar of Japanese Legal Obligations: しなければならない, してはならない, できる

Core examples: しなければならない, してはならない, できる, ものとする, 努めなければならない, みなす, 第三条, 正当な理由なく.

Legal Japanese does not use ordinary “should” casually

In everyday speech, someone may say:

行かなければならない。 I have to go.

In legal and administrative writing, similar forms create duties, prohibitions, permissions, presumptions, and institutional powers. The grammar is not merely moral advice.

A clause like:

申請者は、必要書類を提出しなければならない。

does not mean “it would be good if the applicant submitted documents.” It creates a requirement.

The key principle:

In legal Japanese, modal phrases assign legal force.

You must identify whether a clause creates duty, ban, permission, effort obligation, deemed status, or procedure.

しなければならない: mandatory duty

〜しなければならない

This marks obligation: must do.

Example:

利用者は、変更があった場合、速やかに届け出なければならない。 The user must promptly report any change.

In legal or rule-like writing, this is strong. It assigns duty to a subject.

Learner action: find who is obligated and what action is required.

してはならない: prohibition

〜してはならない

This means must not / shall not.

Example:

許可なく立ち入ってはならない。 One must not enter without permission.

This is formal and strong. In ordinary signs, you may see 禁止. In law-like prose, してはならない is common.

できる: permission or legal power

In everyday Japanese, できる often means can / be able to. In legal Japanese, it can mean may or has authority to.

市長は、必要があると認めるときは、調査を行うことができる。 The mayor may conduct an investigation when deemed necessary.

This does not mean physical ability. It grants legal discretion or power.

Learner action: in legal contexts, read できる as “may / is authorized to” when the subject is an institution or official.

ものとする: deemed rule or formal stipulation

〜ものとする

This often states a rule, assumption, or formal treatment.

申請は、到着した日に受理されたものとする。 The application shall be deemed received on the day it arrived.

It gives legal-administrative effect to a status.

努めなければならない: effort obligation

努めなければならない

This means must endeavor to / must make efforts to. It is weaker than a concrete duty to achieve a result.

Example:

事業者は、安全の確保に努めなければならない。 The business operator must endeavor to ensure safety.

The actor must make efforts, but the phrase may not guarantee a specific result.

みなす: legal deeming

みなす

Means to deem / regard as. In legal language, it creates a formal status regardless of ordinary reality.

提出があったものとみなす。 It shall be deemed submitted.

Learner action: when you see みなす, identify what status is being legally assigned.

Exceptions and conditions

Legal obligations often depend on conditions:

正当な理由なく without justifiable reason

ただし however / provided that

場合を除き except in cases where

These phrases can change the force of the rule. Do not parse the modal phrase without its exceptions.

Example walkthroughs

しなければならない

Mandatory duty.

Learner action: identify subject and required act.

してはならない

Prohibition.

Learner action: identify banned action and scope.

できる

May / is authorized to in legal contexts.

Learner action: do not read only as ability.

ものとする

Formal stipulation/deemed status.

Learner action: find what rule is being set.

努めなければならない

Effort obligation.

Learner action: distinguish effort from guaranteed outcome.

みなす

Legal deeming.

Learner action: status is assigned by rule.

第三条

Article 3.

Learner action: legal texts are organized by numbered articles.

正当な理由なく

Without justifiable reason.

Learner action: exception/justification phrase affects obligation.

Legal-duty parse workflow

1. Identify the legal subject.
2. Identify the action.
3. Locate modal phrase: duty, ban, permission, effort, deemed rule.
4. Check conditions and exceptions.
5. Check penalty or legal effect.
6. Decide whether the clause creates obligation, prohibition, authorization, presumption, or procedure.

Legal modality is not everyday mood

In legal and rule-like Japanese, modal phrases create legal effects. They are not merely personal advice.

The ordinary translation “can” for できる is dangerous in legal contexts. It may mean that an agency has authority, not simply physical ability.

市長は、必要があると認めるときは、資料の提出を求めることができる。 The mayor may require submission of documents when deemed necessary.

This is a power granted to an official.

Subject of obligation matters

Legal Japanese often hides agency behind long noun phrases. Always identify who bears the duty.

申請者は、必要書類を提出しなければならない。 The applicant must submit the required documents.

管理者は、個人情報を第三者に提供してはならない。 The administrator must not provide personal information to third parties.

The subject is not background. It is the legal target.

Exception clauses change everything

Watch for exception markers:

ただし however / provided that

正当な理由なく without justifiable reason

必要がある場合 when necessary

法令に基づく場合を除き except when based on laws and regulations

A duty or prohibition may be narrower than it first appears.

Legal-duty parse, upgraded

For each clause:

1. Identify the legal subject.
2. Identify the required, prohibited, permitted, or deemed action.
3. Mark exceptions and conditions.
4. Note whether できる means ability, permission, or authority.
5. Look for penalty, effect, or procedure elsewhere in the document.
6. Translate after you know the legal function.

Legal Japanese is rigid because consequences depend on scope.

Suggested functions:

1. Duty/prohibition/permission classifier.
2. Subject-action extraction.
3. Exception highlighter: ただし, 除く, 正当な理由なく.
4. Effort vs result label.
5. Plain-language paraphrase.

Final rule

Legal Japanese turns grammar into force.

しなければならない creates duty. してはならない creates prohibition. できる often grants authority. ものとする and みなす create legal status. 努めなければならない creates effort obligation.

In legal texts, modal phrases are not style. They are consequences.