The Schengen Acquis: Abolition of Internal Borders and Integrated External Border Management

The Schengen acquis encompasses the legal framework for the abolition of internal border controls within the participating European states and the establishment of common rules on external border controls, visas, and police cooperation. Originating in the Schengen Agreement of 14 June 1985 and the Schengen Convention of 19 June 1990, the acquis was initially developed outside the EU legal framework by a subset of Member States. It was integrated into the EU legal order by the Treaty of Amsterdam in 1999 and now constitutes a fundamental element of the Area of Freedom, Security and Justice.

The Schengen Agreement and Convention

The Schengen Agreement was signed outside the Community framework by Belgium, France, Germany, Luxembourg, and the Netherlands. The Agreement provided for the gradual abolition of checks at common borders and the introduction of freedom of movement for all persons. It established a framework for compensatory measures, including harmonised external border controls, common visa policy, police cooperation, and mutual assistance in criminal matters.

The Schengen Convention of 1990 implemented the Agreement by establishing detailed rules for the abolition of internal border controls, the conditions for crossing external borders, the harmonisation of visa policies, the responsibilities for processing asylum applications, and police and judicial cooperation. The Convention established the Schengen Information System (SIS) , a common database for alerts on persons and objects relating to border control, police, and judicial cooperation. The Convention also introduced the principle that Member States must verify compliance with entry conditions at external borders and established rules for the temporary reintroduction of internal border controls.

Integration into the EU Legal Order

The Treaty of Amsterdam incorporated the Schengen acquis into the EU legal framework through a Protocol annexed to the Treaties. The Protocol provided that the Schengen acquis would apply to all Member States except the United Kingdom and Ireland, which obtained opt-outs allowing them to maintain their own border controls. Norway and Iceland, as non-EU members of the Nordic Passport Union, were associated with Schengen through a special agreement. Subsequent association agreements extended Schengen to Switzerland, Liechtenstein, and (partially) to Denmark, which has an opt-out from justice and home affairs but participates in Schengen through an intergovernmental arrangement.

The Amsterdam Treaty provided that the Council, acting unanimously, would replace the Schengen acquis with EU legislation, applying the appropriate EU decision-making procedures. The integration of Schengen into the EU framework brought the Schengen rules under the jurisdiction of the CJEU and ensured that the Schengen acquis could be developed through the ordinary legislative procedure. The Schengen Borders Code, adopted in 2006 as Regulation (EC) No 562/2006 (replaced by Regulation (EU) 2016/399), codified the rules on border controls and established a common legal framework for internal and external borders.

The Schengen Borders Code

Regulation (EU) 2016/399 (the Schengen Borders Code) establishes the legal framework for border controls within the Schengen area. The Code provides that internal borders may be crossed at any point without any checks on persons, regardless of nationality. External borders may be crossed only at authorised border crossing points during fixed opening hours, and third-country nationals must satisfy entry conditions: possession of a valid travel document, a valid visa if required, justification of the purpose and conditions of stay, sufficient means of subsistence, absence of an alert in the SIS, and no threat to public policy, internal security, public health, or international relations.

The Borders Code establishes the Schengen evaluation mechanism to monitor Member State compliance with Schengen rules. The evaluation mechanism, originally based on peer review and subsequently reformed in 2015, requires periodic evaluations of all Member States’ performance in border management and the application of Schengen standards. Member States with deficiencies in external border management may be required to take corrective action, and the Commission may make recommendations to address identified weaknesses.

Temporary Reintroduction of Border Controls

The Schengen Borders Code permits the temporary reintroduction of internal border controls in the event of a serious threat to public policy or internal security. Under Article 25 of the Code, a Member State may reintroduce border controls for a renewable period of up to 30 days for foreseeable events (extendable up to six months). Under Article 28, a Member State may reintroduce controls for a period of up to ten days (extendable in 20-day increments up to two months) in cases requiring urgent action.

The temporary reintroduction of internal border controls has been used with increasing frequency since 2015. Member States have invoked Articles 25 and 28 in response to the migration crisis, terrorist attacks, and the COVID-19 pandemic. The Commission has issued opinions on the necessity and proportionality of such measures and has encouraged Member States to use targeted controls rather than systematic border checks. The proliferation of temporary controls has raised concerns about the erosion of the Schengen area and the need for reform of the rules governing internal border checks.

The Schengen Information System

The Schengen Information System (SIS) is the largest shared security database in Europe, containing alerts on persons and objects relevant to border control, police cooperation, and judicial cooperation. SIS alerts cover wanted persons for arrest or surrender, missing persons, persons sought for judicial proceedings, persons subject to discreet surveillance or specific checks, and objects sought for seizure or use as evidence (including vehicles, documents, and firearms).

SIS has undergone three generations of development. SIS I operated from 1995, SIS II became operational in 2013 with enhanced functionality, and further reforms have expanded the categories of alerts and improved interoperability with other EU information systems. SIS is governed by Regulation (EU) 2018/1860 (entry/exit system), Regulation (EU) 2018/1861 (border checks), and Regulation (EU) 2018/1862 (police and judicial cooperation). Access to SIS data is strictly limited to competent national authorities, and data protection safeguards are provided by Directive (EU) 2016/680.

The Integrated Border Management Framework

The EU has developed an Integrated Border Management (IBM) framework to coordinate national border authorities, Frontex, and other EU agencies in managing external borders. The European Border and Coast Guard Agency (Frontex) , established in 2004 and substantially reinforced in 2016 and 2019, coordinates European-level operational cooperation, manages the European Border and Coast Guard standing corps, conducts risk analysis, and may participate in joint operations and rapid border interventions.

The evolution of Schengen from an intergovernmental agreement among five Member States to a fundamental component of the EU legal order reflects the progressive integration of core state functions at European level. The Schengen area remains the world’s most advanced framework for the abolition of internal border controls, combining freedom of movement with collective responsibility for external border security. The challenges of the migration crisis and security threats have prompted ongoing reform of the Schengen governance framework, including proposals for enhanced border surveillance, improved return procedures, and strengthened solidarity mechanisms for Member States facing disproportionate migratory pressure.