Proving authority: AI agents under Swiss, German and Austrian law

Key points

• Whoever claims an authority must be able to prove it in a dispute.
• A presented mandate makes the limits visible to both sides.
• Verifiable evidence answers six questions: who, for whom, what, when, still valid, acted on accordingly.
• Authorizations usually require no form; a signed mandate serves mainly as proof.

Why the proof is decisive

German law puts it in a nutshell: under Section 179 BGB, an agent is liable unless it proves its authority. In Switzerland and Austria, too, whoever claims an authority it cannot prove bears the risk (Article 39 of the Code of Obligations, Section 1019 ABGB). Proof of authority is therefore not a formality but the core of every dispute about actions taken on someone's behalf.

With AI agents, the question becomes sharper. Agents act fast, often and without a person seeing every action. A log in one's own system helps little because the other side cannot verify it. What is needed is evidence that can be recomputed independently.

Communication: when the third party knows the limits

All three legal systems protect the reliance of third parties who were entitled to assume an authority. In Switzerland, the scope of an authorization communicated to a third party follows that communication (Article 33 paragraph 3 of the Code of Obligations); Germany and Austria have comparable principles on apparent authority.

For agents, this leads to a practical rule: if the agent presents its mandate to the other side, the limits are visible to both. The merchant knows what is allowed and can decline actions outside it. The principal can show which limits it set. Both gain clarity.

What verifiable evidence must contain

Evidence of an agent's authority answers six questions. If one answer is missing, a gap remains that counts against whoever relies on the authority in a dispute.

1. Who is the agent? Identifier and key, bound through key binding.
2. On whose behalf does it act? The principal, named unambiguously.
3. What may it do? Action types, amount limits, counterparties.
4. When does it apply? Start and end of validity.
5. Does it still apply? Status through a status list.
6. Was it acted on accordingly? Decision and receipt for the specific action.

Form and evidential value

Most transactions require no particular form, and an authorization usually needs none either. Where the law requires written form, a qualified electronic signature is generally equivalent to a handwritten one: in Switzerland under Article 14 paragraph 2^bis of the Code of Obligations, in Germany under Section 126a BGB and in Austria under Section 4 of the Signature and Trust Services Act.

A signed mandate usually does not need to meet this form to take effect. Its value lies in proof: the signature shows who issued it and that it is unchanged. Courts assess such evidence freely. The more clearly origin, content and time are proven, the greater its weight.

How KYA verifies authority

KYA checks every piece of evidence in ten steps: format, cryptographic integrity, issuer origin, binding of agent and principal, mandate validity, scope of action, delegation, revocation, execution binding and point in time. Each step has its own status, and the overall verdict is valid, invalid or indeterminate.

The levels KYA-A0 to KYA-A4 show how much is proven. For a payment, it should at least be proven that the mandate was valid, the action was within scope and no revocation applied. For disputes, an independently anchored point in time is added.

Practice: from paper to data record

Many companies today work with written authorizations, signing rules and roles in IT systems. These rules can be carried over to agents. A mandate per task replaces blanket access, a status list replaces revocation by email, and a receipt replaces the log.

It is important to tie the issuing of mandates to the same internal rules that govern authorizations today: who may issue mandates for the company, up to which amount, with which validity? These rules should be documented so the proof holds internally as well.

Common gaps in evidence

The most common gap is a mandate without binding to the agent: whoever holds it can present it. The second is a missing revocation status, leaving open whether the mandate still applied at the time of the action. KYA reports both gaps in the certificate.

Frequently asked questions

Does an authorization for an AI agent need a particular form?

Usually not. Form requirements apply only to certain transactions. A signed mandate is above all evidence that proves the origin, content and time of the authority.

What is apparent authority for AI agents?

If the principal created the appearance that its agent may take an action, it may have to accept this, depending on the legal system. A presented mandate with clear limits reduces this risk.

Who has to prove the authority?

Usually whoever relies on it. German law states this explicitly for the agent in Section 179 BGB.

Does a KYA certificate replace notarization?

No. A certificate proves the result of a technical verification. Where the law requires a particular form, it does not replace it.

How long should a mandate be valid?

As short as practical for the task. Short validity limits the damage in case of abuse and makes clear which limits applied at which time.

What applies if a mandate is revoked during an action?

The status at the time of the action is decisive. That is why KYA checks revocation against the status list and records the verification time in the certificate.

General information, not legal advice. The statutes and the circumstances of each case are decisive.

Sources

1. Obligationenrecht (OR), Art. 14 und 33: https://www.fedlex.admin.ch/eli/cc/27/317_321_377/de#art_33
2. BGB, § 126a und § 179: https://www.gesetze-im-internet.de/bgb/__179.html
3. Signatur- und Vertrauensdienstegesetz (SVG), Österreich: https://www.ris.bka.gv.at/GeltendeFassung.wxe?Abfrage=Bundesnormen&Gesetzesnummer=20009545
4. SD-JWT VC (IETF): https://datatracker.ietf.org/doc/draft-ietf-oauth-sd-jwt-vc/