Fundamentals

Legal uncertainty: what it is, why it arises, and how it affects the rule of law

By Daniel Sardá · Published on July 12, 2026 · Updated on July 15, 2026

9 min read1,795 words

Legal uncertainty arises when knowing the rules is no longer enough to reasonably anticipate how public authorities will act. Understanding its causes helps distinguish it from legitimate legal change and unavoidable uncertainty.

Legal uncertainty is the loss of reasonable confidence about what the law requires and how it will be applied. It does not refer to crime or fear for one's physical safety—that belongs to the field of public safety—but to a failure in the relationship among rules, authorities, and the people subject to them.

Consider a hypothetical case. A person obtains a permit under published criteria, invests resources, and begins a lawful activity. Months later, an agency revokes the permit based on an instruction that was never published and, moreover, is not applied to other similar cases. The problem is not simply that the decision is unfavorable. It is that determining which rule governs, why it is being applied that way, and where the decision can be reviewed becomes difficult.

The Costa Rican Judiciary's Diccionario Usual places uncertainty, distrust, and unpredictability at the heart of the concept. That institutional definition provides a useful starting point. More broadly, legal uncertainty exists when people cannot plan their conduct with sufficient foresight about its legal consequences, whether because of flaws in the rules, inconsistent administrative action, or judicial responses that are difficult to reconcile.

Key idea: Legal uncertainty does not mean losing a case or facing a demanding rule. It means being unable to reasonably know or anticipate the rules and how they will be applied.

Reasonable predictability, not absolute certainty

No legal system can promise an obvious answer to every dispute. Laws use general concepts, facts change, and judges must interpret them. Two experts may disagree in good faith about the scope of a rule without creating a crisis of legal certainty.

The sensible standard is reasonable predictability: rules should be accessible and sufficiently clear to guide conduct, while their application should remain consistent enough to make outcomes foreseeable within a reasonable range. The Venice Commission includes accessibility, foreseeability, stability, and consistency among the elements of legal certainty associated with the rule of law.

This also prevents stability from being confused with immobility. A society needs to reform unjust, outdated, or ineffective laws. Legal change is compatible with legal certainty when it follows known procedures, is published, provides an adequate transition where appropriate, and respects applicable safeguards. The problem is not change itself, but change that is opaque, abrupt, or capable of frustrating legitimate expectations without justification or avenues for redress.

Nor does the protection of legitimate expectations create a general right to keep legislation unchanged. Its scope varies by legal system, but it protects qualified expectations created in good faith by state action. It requires authorities to consider the justification for change, its effects, and transitional measures; it does not turn every individual expectation into a veto over reform.

How legal uncertainty arises

The loss of predictability rarely has a single cause. It may begin in the wording of a rule and worsen during its application. A reasonably clear rule can also become uncertain through selective administrative decisions or persistently incompatible judicial interpretations.

Inaccessible, vague, or unstable rules

The first dimension concerns the rules themselves. It is difficult to plan one's conduct when provisions are not published accessibly, contradict one another, or delegate decisions without specifying purposes or criteria. Complexity alone does not prove legal uncertainty: some fields require technical regulation. The relevant warning sign appears when even a diligent person cannot determine what is required, or when an authority enjoys such open-ended latitude that the rule ceases to constrain it.

Timing and transition also matter. An obligation announced in advance, with clear rules for pending cases, does not have the same effect as a requirement suddenly applied to conduct that has already occurred. Retroactivity deserves particular caution, but its legal treatment varies by subject and jurisdiction; in criminal law, protection against retroactive punishment is especially strict.

Inconsistent or selective administration

Rules become real through permits, taxes, penalties, benefits, and procedures. Legal certainty therefore depends on more than the quality of statutory language. An administration can undermine it by changing criteria without explanation, delaying decisions indefinitely, demanding documents that were not prescribed, or treating equivalent cases differently without a public reason.

This does not mean eliminating all discretion. Complex administrations need to adapt decisions to circumstances that lawmakers cannot fully anticipate. Rule-bound discretion has defined purposes, relevant criteria, a duty to give reasons, and review mechanisms. Arbitrary state power, by contrast, replaces those limits with a will that is difficult to control.

From the perspective of individual liberty, the difference is decisive. When an authorization depends on public rules, a person can comply with them and challenge their application. When it depends on favors or ad hoc decisions, people become more dependent on those who wield power.

Inconsistent or ineffective judicial responses

Courts must resolve genuine disagreements, so some evolution in case law is normal. A different ruling does not by itself prove arbitrariness: it may reflect different facts, stronger reasoning, or a reasoned change in the law.

The problem arises when equivalent cases persistently receive incompatible outcomes without explanation or effective means of correction. It also appears when review comes too late to remedy the harm or when a final judgment can easily be ignored. Predictability requires independent judges and avenues of appeal, but also public reasons that make it possible to understand why a case was decided as it was.

Key idea: A clear rule can become uncertain through selective enforcement; a rule-bound administration can lose predictability if judicial review is inconsistent. These dimensions reinforce one another.

Signs that reveal legal uncertainty

Public distrust is relevant evidence, but perception alone is not enough to establish legal uncertainty. A diagnosis must be tested against observable practices. The most important signs include:

• rules that are not published or whose content is difficult to determine;
• abrupt changes that affect established situations without a transition or sufficient justification;
• official powers defined without clear purposes, criteria, or safeguards;
• requirements introduced during a procedure that were not specified beforehand;
• selective application of the same rule to comparable cases;
• incompatible decisions that lack reasons or an effective avenue for review.

No single sign necessarily proves a systemic failure. An error can be corrected; a judicial divergence may be reasoned; an emergency may require a rapid response. What matters is the frequency and severity of the problem, the absence of justification, and the institution's ability to correct it.

Distinguishing perception from evidence guards against two errors. The first is minimizing a widespread experience of powerlessness. The second is using “legal uncertainty” to discredit every unpopular decision or any regulation that imposes costs.

Its effects on rights and decision-making

The most immediate consequence is practical: people lose the ability to make informed decisions. If they do not know what conditions will preserve a permit, which contractual terms will be enforced, or which procedure will protect property, they must devote more resources to managing risks generated by the system itself.

This affects contracts, personal projects, associations, and business decisions. It can make planning and investment more difficult, but economic outcomes have many causes: no particular growth outcome should be attributed to legal uncertainty alone. The more cautious claim is that it raises risks and makes long-term agreements harder.

The harm is not confined to the economy. A person may forgo exercising a right out of fear that a rule will change selectively or that review will never come. Another may seek intermediaries with privileged access instead of following a public procedure. Institutional uncertainty thus alters incentives and encourages relationships of dependence.

General rules serve a protective function here. The generality of the law reduces the scope for exceptions designed to target particular people and makes unequal treatment more visible. It does not guarantee that a rule is just, but it makes it harder for authorities to change course according to the identity or influence of the person affected.

Warning: A perfectly predictable rule can still be unjust or oppressive. Legal certainty is necessary for the rule of law, but it is no substitute for fundamental rights or the moral evaluation of law.

Legal certainty and limits on power

Legal certainty is part of the rule of law because it makes the exercise of power subject to rules. Publicity, legality, reasoned decisions, review, and enforcement of court judgments ensure that individuals do not depend entirely on the will of the official in office.

This relationship expresses a classical liberal insight: liberty requires a sphere in which each individual can make plans without seeking permission at every step or fearing unpredictable intervention. Public and general rules do not eliminate power, but they make it more controllable. They allow people to know its boundaries, demand reasons, and appeal a decision.

Yet the mere existence of many rules does not amount to the rule of law. A government could regulate every aspect of life through published provisions and still violate basic liberties. Nor is a solemn constitution enough if ordinary authorities disregard its limits. Predictability must be joined by checks on power, equality before the law, access to judicial protection, and respect for rights.

How to reduce uncertainty without freezing the law

No formula can eliminate all uncertainty. But institutional conditions can keep it within limits compatible with an open society:

• publish relevant rules and decisions in an accessible form;
• draft rules with sufficient clarity and coordinate provisions that may conflict;
• justify changes and provide transitions when legitimate expectations are affected;
• constrain discretion through defined purposes, criteria, reason-giving, and safeguards;
• apply rules consistently to comparable cases;
• ensure independent review and mechanisms to correct persistent divergences.

These measures are not meant to turn law into an automatic machine. Flexibility may be necessary to respond to exceptional situations and avoid manifestly inequitable outcomes. But the greater the margin for decision, the stronger the demands for reasons, transparency, and review should be.

Key idea: A legally secure system does not promise that rules will never change. It promises that legal change and enforcement will remain subject to known procedures, reasons, and limits.

The final test is not whether a person can anticipate every judgment or administrative decision. It is whether that person can know the relevant rules, reasonably trust that similar cases will receive similar treatment, and turn to a body capable of reviewing abuse. Where that possibility weakens, legal uncertainty ceases to be a vague impression and becomes an institutional problem of liberty and limits on power.

Sources consulted

• Costa Rican Judiciary, “Inseguridad jurídica,” *Diccionario Usual*.
• Venice Commission, *Rule of Law Checklist* (2016).
• Venice Commission, *Report on the Rule of Law* (2011).
• Venice Commission, CDL(2020)033.
• World Justice Project, “Regulatory Enforcement”.