I. The Constitutional Text - The Triple Foundation

1. Art.18.4 CE - The source of digital identity right

The law shall limit the use of informatics to guarantee honour and personal and family privacy and the full exercise of rights.

This article is unique in Europe. The Constituent Assembly in 1978 foresaw informatics. Tribunal Constitucional interpreted it as creating a new fundamental right.

2. Art.18.1, 18.2, 18.3 CE - Privacy, domicile, secrecy of communications
Any digital identity system that allows identification, tracking or profiling affects Art.18.

3. Art.105 and 103 CE - Right to interact with Administration
Administration must regulate procedure by law. Digital identity is the gateway to that right. If system excludes, it violates effective administrative action.

4. Art.9.2 and 14 CE - Equality and inclusion
Digital identity cannot create digital divide. Administration must ensure non-digital alternative remains.

From these, Tribunal Constitucional built the doctrine.

II. The Foundational Case Law That Defines Digital Identity

STC 254/1993, 20 July 1993 - First data protection case:
First time TC says Art.18.4 contains a positive right to control your own data - derecho de autodeterminación informativa. Citizen can know who has his data and for what.

STC 292/2000, 30 November 2000 - The Magna Carta of Digital Identity in Spain:
This is the leading case in all Spanish digital law. TC declares:

Data protection is not limited to intimate data, but to any type of data whose knowledge or use by third parties may affect rights. It is an autonomous fundamental right independent of privacy, honour and image.

It creates 3 powers for citizen:
a) Right to consent to collection
b) Right to know purpose
c) Right to oppose and cancel

Every DNIe, Cl@ve, or wallet system must comply with this. If it processes data without consent or without purpose limitation, it is unconstitutional, not just illegal.

TC says Art.18.4 protects even public data if its aggregation creates identity profile.

STC 99/2019, 18 July 2019 - Right to gender identity as part of digital identity:
Trans minor claimed right to change name/gender marker in DNI. Supreme Court raised cuestión de inconstitucionalidad. TC ruled Art.18.1 privacy includes right to self-determined gender identity and its reflection in official identity documents. Digital identity must reflect real identity, not assigned one.

STC 124/2024 and STS on Justicia Digital - Digital Legal Security:
Since 2016, Justicia Digital platform requires Cl@ve Justice and eIDAS certificate to file lawsuits. Tribunal Supremo 2024 confirmed this is constitutional under Art.24 right to effective judicial protection IF system guarantees seguridad jurídica digital - identification must be high assurance and alternative filing must exist for digital gap.

III. The Spanish Digital Identity System - 4 Layers

Spain has 4 constitutional layers, not one:

Layer 1 - Legal Identifier - DNI - Organic Law:
DNI is regulated by Organic Law - LO 4/2015 on Citizen Security and RD 414/2015. Obligation to have it from 14 years. This is the root identity. Art.8: DNI is sufficient to prove identity and nationality.

Layer 2 - Electronic Version - DNIe 4.0

• Only Spanish eID notified to EU under eIDAS Regulation - Notified 7 November 2018, OJEU C401/08, assurance level HIGH.
• Contains 2 certificates: authentication and qualified electronic signature under eIDAS.
• Chip NFC readable.
• Constitutional status: voluntary use of electronic function. Art.9 RD 414/2015: No citizen can be forced to use electronic chip if he does not have reader. Physical DNI remains valid.

Layer 3 - Federation System - Cl@ve

This is where most citizens interact.

Cl@ve is not a separate identity, it is federation of:

• Cl@ve PIN - temporary password sent to mobile
• Cl@ve Permanente - user + password + OTP
• Cl@ve Firma - remote qualified signature in cloud HSM
• Certificado digital FNMT

Legal basis: Law 39/2015 Art.9 and 10 - systems of identification for relations with Administration.

Cl@ve 2.0 since 2022 is aligned with eIDAS - allows login to Spanish administration and via eIDAS node to 27 EU States.

Critical constitutional distinction: Cl@ve is NOT notified as eID under eIDAS - only DNIe is. European Commission eID User Community page confirms: Spanish entry is only DNIe. Cl@ve is national interoperability layer.

Layer 4 - New Mobile and EU Wallet - MiDNI + Cartera Digital / EUDI Wallet

MiDNI App - Since 2 April 2024: Royal Decree 1555/2023. Allows DNI to be carried on mobile with same legal validity as physical card for in-person ID. Since April 2, 2025, hotels and businesses are legally required to accept MiDNI as valid ID under new traveler registration law. Based on eIDAS 2.0 framework.

Cartera Digital - Spanish EUDI Wallet implementation - Announced project category: Under eIDAS 2 Regulation 2024/1183, Member States must make EUDI Wallet available by 2026. Spain's implementation is called Cartera Digital. It will hold Person Identification Data (PID) + Qualified Electronic Attestations of Attributes - driving licence, degree, bank account.

Art.6 eIDAS 2: use of wallet must be voluntary. Art.12: GDPR compliance mandatory. This codifies STC 292/2000 at EU level.

Spain was first country to have eIDAS node available and one of first to notify DNIe - per Joinup EU Digital Government Factsheet Spain.

IV. Constitutional Principles That Regulate All Systems

From LOPDGDD 3/2018 + eIDAS 2 + STC 292/2000, any Spanish digital identity system must meet 7 constitutional requirements:

1. Reserva de Ley Orgánica - Art.18.4 and 81 CE:
Regulation of fundamental right to data protection must be by Organic Law. This is why LOPDGDD is Organic Law 3/2018. A Royal Decree cannot create new digital identity.

2. Voluntariness - Art.6 eIDAS 2 + Art.9.2 CE:
Citizen must have right to choose wallet. Parliamentary question P-004426/2025 EU Parliament: Commission confirmed wallet use based on voluntary choice. Administration cannot make digital identity mandatory for accessing essential public services. Must keep face-to-face channel - Law 39/2015 Art.12.

3. Purpose Limitation and Minimization - STC 292/2000:
System can only request data strictly necessary for identification. Example: hotel cannot read full DNIe chip, only name and expiry - principle of selective disclosure in EUDI Wallet.

4. Inclusion and Accessibility - Art.49 CE + RD 1112/2018:
System must be accessible for disabled, elderly, digital gap. AEPD fined private provider Yoti €950,000 in 2026 for biometric processing non-compliant - consent architecture and retention - leading Yoti to remove app from Spanish stores 10 Sept 2026 pending appeal. Shows AEPD as enforcer of constitutional standard.

5. State Monopoly + Decentralization - Art.149.1.11 + 18.4:
Only State can define official digital identity. But Autonomous Communities can develop own Cl@ve integration via EID4Spain project - connecting local eServices.

6. Security and Qualified Trust - eIDAS Regulation Art.8:
For high-risk transactions - taxes, justice - level High required - DNIe or qualified certificate. Cl@ve PIN only allowed for low risk.

7. Right to Digital Disconnection and Digital Education - LOPDGDD Title X:
Arts.83-97 LOPDGDD create digital rights: right to be forgotten, to digital education, to not be subject to solely automated decisions - directly applicable to digital identity profiling.

V. Recent Litigation - Where System Fails Constitution

AEPD vs Catalan Judges Leak - STS 9 Jan 2024:
Photos of sovereignist judges leaked. AEPD closed investigation. Supreme Court ordered reopen - processing of judicial data without authorization violates Art.18.4. Shows identity data of judges also protected.

AEPD PS/00221/2020 - Right to access DNI data:
Citizen requested access to data processed by company that scanned DNI. AEPD required company to provide access. Right of access includes right to know which DNI data was stored.

Age Verification Wallet - Porn access - 2024 initiative:
Spanish government plans digital identity wallet to limit minors access to adult content. Constitutional challenge: must pass STC 292/2000 proportionality - is age verification necessary and least intrusive? EUDI Wallet selective disclosure (prove >18 without revealing identity) is constitutional solution.

Summary Model

Spain constitutional model is:

DNI [Organic Law] → DNIe [eIDAS High, notified] → Cl@ve [federation, Law 39/2015] → MiDNI / EUDI Wallet [eIDAS 2, voluntary]

All under STC 292/2000 autonomous fundamental right to data protection.

Any system that forces citizen to use biometric, that retains data longer than necessary, or that excludes non-digital citizen, is not just illegal - it is unconstitutional under Art.18.4 and can be challenged via recurso de amparo to Tribunal Constitucional.