What the Law Leaves Open

Reasonable, proportionate, disproportionate: what these terms actually do

Disability equality legislation in Great Britain, and its equivalents across most developed jurisdictions, does not hand disabled people a fixed list of entitlements. It hands them a principle. The Equality Act 2010 requires employers and service providers to make reasonable adjustments. The Public Sector Equality Duty requires proportionate action. The European Accessibility Act uses disproportionate burden as the threshold below which obligations can be waived. None of these terms is defined with precision in statute, and that is not an accident.

The flexibility is deliberate. Legislators recognised that what is reasonable for a multinational bank is not reasonable for a sole trader; that a proportionate response to a listed building's access constraints differs from one applied to a new-build office. The elastic language lets the law scale. It also lets organisations negotiate, delay, and — where scrutiny is weak — avoid.

How the concepts have been interpreted

In Great Britain, employment tribunals and courts have built up a body of case law around reasonableness. Several principles have emerged consistently. The size and resources of the organisation matter: a large employer is expected to spend more and adapt more than a small one. The effectiveness of the adjustment matters: a change that would provide only marginal benefit can, in principle, be declined. The disruption an adjustment causes to other employees or to the operation of a service is a legitimate factor — though courts have historically been unimpressed when that disruption is speculative rather than demonstrated.

Crucially, cost alone has rarely been accepted as a complete justification for non-compliance. Tribunals have repeatedly found that employers and service providers underestimated what was reasonable when they looked only at headline expenditure and ignored the cost of not adjusting — lost productivity, staff turnover, legal exposure, and the wider obligations the Equality Act imposes alongside the adjustment duty.

The disproportionate burden defence in web and app accessibility — codified in the UK's Public Sector Bodies Accessibility Regulations — requires organisations to conduct and publish an assessment before invoking it. In practice, many do not. The defence exists; the accountability mechanism around it is thin.

The terrain that remains genuinely open

Three areas consistently produce the most uncertainty. First, the point at which an adjustment becomes unreasonable is not a fixed line; it shifts with an organisation's circumstances, and those circumstances change. An adjustment declined during a period of financial difficulty may become perfectly reasonable two years later — but there is no automatic trigger requiring reassessment.

Second, the duty to make reasonable adjustments is anticipatory in the context of service provision, meaning providers should not wait for a disabled person to appear before thinking about access. How far in advance, and with what specificity, remains contested. Third, indirect discrimination — where a neutral policy disproportionately disadvantages disabled people — sits alongside the adjustment duty but is assessed differently, and the two can be confused in practice, sometimes to a claimant's cost.

None of this means the law is toothless. The concepts of reasonableness and proportionality give courts and tribunals real room to find against organisations that have done little, spent little, and thought little. What they do not provide is a simple checklist. The law draws a wide circle and says: stay inside it. Working out exactly where the boundary runs is why adjustments stall in organisations that have no one whose job it is to find out.