Belgium: Courts Can Strike Down CBAs If They Violate Constitutional Equality and Non-Discrimination Principles

In a landmark ruling delivered on 23 March 2026, Belgium’s Court of Cassation confirmed that collective bargaining agreements (CBAs), even those elevated to the status of binding law by Royal Decree, can be struck down by courts if they conflict with the constitutional principles of equality and non-discrimination. The case arose from trade union elections in which a sector-level CBA effectively barred an entire category of employees from participating. The Court’s decision has significant implications for employers, trade unions, and HR professionals across Belgium.

Background: trade union elections and who can vote

The case centred on a company falling under Joint Committee 209 (white-collar employees in the metal industry). A sector-level CBA of 6 February 1996, made generally binding by Royal Decree, governed the trade union delegation for white-collar staff. That CBA restricted the right to vote, stand as a candidate, and be counted in the calculation of trade union mandates to employees covered by a collectively agreed wage scale and job classification scheme. Employees who sat outside that classification system, including engineers and other non-classified senior staff, were entirely excluded.

An internal “engineers’ group” had existed since 1989 to represent this non-classified cadre, negotiating directly with management on their behalf. The employer considered this sufficient.

Events came to a head in late 2015 and early 2016. In November 2015, trade unions CNE and Setca formally requested that the 2016 social elections be opened up to non-classified employees. The employer refused and confined the electoral roll to classified employees only. In March 2016, the CSC submitted a candidate list that included Mr D., a non-classified employee. The employer declined to publish the list, citing the 1996 CBA. Following the elections of 12 May 2016, the CSC, CNE, and Mr D. brought proceedings before the Labour Tribunal of Charleroi.

The legal journey: from Charleroi to Cassation

The case wound its way through the Belgian courts over several years:

• The Labour Tribunal of Charleroi (first instance, judgement of 5 May 2018) dismissed the unions’ claims in full, finding the main claim (annulment of the elections and re-run) unfounded.
• The Labour Court of Appeal of Mons reversed that judgement entirely on 15 March 2019. It annulled the 12 May 2016 elections and declared Articles 2, 6, 8, 9 and 12 of the 1996 CBA null and void for incompatibility with Articles 10 and 11 of the Belgian Constitution.
• The appeal court ordered the employer to organise new elections within two months, open to all eligible employees — including non-classified staff — with the exception of senior management. It further held that every employee must be counted when calculating the number of trade union mandates. The elected representatives from the 2016 elections were allowed to remain in post until the new delegation was installed.
• The employer brought the matter before the Court of Cassation.

 

The employer’s arguments: why CBAs should be untouchable

Before the Court of Cassation, the employer advanced three main lines of argument:

1. No horizontal effect. Articles 10 and 11 of the Constitution, which guarantee equality and prohibit discrimination, only bind the State in its relations with citizens (so-called “vertical” effect). They do not apply directly between private parties such as employers and employees. Therefore, they cannot serve as a basis for annulling CBA provisions in a private-law dispute.
2. Hierarchy of norms. The 1996 sector-level CBA had been made generally binding by Royal Decree. Framework CBA No. 5, the cross-industry agreement on trade union delegations, concluded in the National Labour Council (NAR/CNT) in 1971 was not made binding by Royal Decree. The employer argued that a higher-ranking norm (the 1996 CBA, backed by Royal Decree) could not be overridden by a lower-ranking one (CBA No. 5).
3. Proportionality, context, and inadequate reasoning. Even if a legality review were permissible, the employer argued that non-classified employees are not in a comparable situation to classified employees. Their pay is determined differently, and they are represented through different structures (the engineers’ group) that can effectively participate in collective bargaining. The Labour Court of Appeal had, therefore, failed to engage adequately with proportionality arguments, had not sufficiently explained why the situations were comparable, and had not addressed the actual functioning of the engineers’ group in practice. This, the employer argued, amounted to a breach of the duty to state reasons.

The Court of Cassation’s ruling: courts must review CBAs against the Constitution

The Court of Cassation rejected all three arguments and confirmed the Labour Court of Appeal’s approach in full.

On horizontal effect: The Court drew a careful distinction between two legal operations that are easy to confuse. The Labour Court of Appeal had not applied Articles 10 and 11 of the Constitution directly to the relationship between the employer and Mr D. That would indeed be horizontal effect, which is not recognised in Belgian law for constitutional provisions. Instead, the appeal court had assessed whether the CBA itself, as a legal norm, was compatible with superior norms. The Constitution served as the benchmark for that assessment, not as a rule directly binding on private parties. This is a classical “legality review,” a function courts have always exercised.

The legal basis for this review is the combination of two provisions:

• CBA provisions that are contrary to mandatory law are null and void. (Article 9 of the CBA Act of 5 December 1968)
• Courts must refuse to apply acts (including delegated legislation and regulatory instruments) that are not in conformity with the law. (Article 159 of the Belgian Constitution)

Together, these provisions oblige courts to review whether CBA provisions comply with higher-ranking norms, including the Constitution. This is not a novel principle; it is the normal operation of the legal hierarchy.

 

On hierarchy of norms and CBA No. 5: The Court rejected the hierarchy-of-sources argument by clarifying precisely what the Labour Court of Appeal had and had not decided. The appeal court had not found that CBA No. 5 prohibits sector-level CBAs from restricting the scope of trade union participation. Rather, it identified the general principles that CBA No. 5 embodies: that all trade-union-affiliated employees have the right to be represented by a trade union delegation before their employer, and that the purpose of that framework instrument is to ensure every such employee enjoys that representation in practice. A sectoral CBA that prevents union members from enjoying rights that normally and legitimately attach to trade union membership does two things simultaneously: it erects a barrier to freedom of association by discriminating between comparable categories of employees without objective and reasonable justification and it violates Articles 10 and 11 of the Constitution. The 1996 CBA was, therefore, not found to violate CBA No. 5 as such, but to violate the constitutional provisions, with CBA No. 5 serving as contextual backdrop that illuminated why the constitutional violation occurred. The hierarchy argument therefore missed the point entirely.

 

On proportionality and the engineers’ group: The Court confirmed a principle of particular practical significance: a legality review of a sectoral norm must be conducted in the abstract, at the level of the norm itself, not by reference to how a particular employer has arranged matters in practice. Whether or not the engineers’ group functioned adequately as a representative body at this specific company was therefore irrelevant to whether the 1996 CBA’s provisions were lawful as a matter of general application.

 

Why the distinction was unjustifiable

The Court accepted the Labour Court of Appeal’s substantive finding: employees covered by a collectively agreed wage scale and those without such a classification are in a comparable situation for the purposes of trade union participation. Both are trade-union-affiliated employees of the same employer; their method of pay determination does not justify their exclusion from the entire electoral process.

The 1996 CBA’s distinction — restricting voting rights, candidacy, and mandate calculation to the first category alone — lacked the objective and reasonable justification required by Articles 10 and 11 of the Constitution. A difference in treatment is only permissible where there is a legitimate aim and a reasonable relationship of proportionality between that aim and the measure employed. The blanket exclusion of non-classified employees from all aspects of the trade union election failed that test.

What does this mean in practice?

This judgement has consequences that extend well beyond the metal industry or the facts of this specific case. Here are the key points for employers, HR professionals, and trade unions:

 

1.  CBAs are not legally untouchable A collective bargaining agreement, even one rendered generally binding by Royal Decree, is not immune from judicial review. Courts can and must set aside CBA provisions that conflict with the Constitution or other higher-ranking legal norms.

 

2.  Compliance with a CBA is not enough An employer who follows the letter of a sector-level CBA to the word is not automatically protected against challenge. If the CBA provision itself is unlawful, compliance with it provides no defence.

 

3.  Distinctions between employee categories must be justified Any CBA provision that treats categories of employees differently, particularly in relation to fundamental rights such as trade union participation, must rest on objective and reasonable justification. Blanket exclusions based on pay determination method are unlikely to meet that standard.

 

4.  Internal representation structures do not affect the legality analysis The existence of an alternative internal representative body (such as an engineers’ group) is irrelevant to whether a sectoral norm is lawful. The legality review concerns the norm in the abstract; company-specific practice is not taken into account.

 

5.  Constitutional principles shape collective bargaining, even indirectly Articles 10 and 11 of the Belgian Constitution do not apply directly between private parties. But through the mechanism of legality review, they do significantly constrain the content of CBAs. In practical terms, constitutional equality principles are very much present in the collective bargaining landscape.

 

Source: Court of Cassation, 23 March 2026  |  Cases S.19.0047.N / S.19.0047.F