Why not all international wills are contestable and how to know before litigating

In forensic practice, few subjects generate as many misunderstandings as succession with an international element.

It is enough that the deceased resided outside of Spain, made a will before a foreign authority, or left assets in several countries for a widespread but mistaken idea to appear: that such a will is, by definition, more vulnerable, more doubtful, or more easily challenged.

The correct starting point is different. In private international law, internationality is not a flaw; it is simply a legal fact that requires identifying which law governs the succession, which authority is competent, and how the validity of the document in Spain must be proven.

A foreign will is not contestable simply because it is foreign, but only when there is a specific legal ground for invalidity or ineffectiveness . In other words, the fact that it is foreign does not replace the grounds for the claim.

The most frequent mistake: confusing “international will” with “suspect will”.

This error stems, in part, from transferring purely internal categories to the international level.

In a cross-border succession, it is not enough to say that a will "does not fit" into the Spanish succession logic.

First, it's necessary to determine whether the case is actually subject to Spanish law. And often it won't be.

In general, the dominant regulatory framework in Europe responds to a logic of conservation and legal certainty.

International succession is not examined from a presumption of nullity, but rather from the need to establish a single governing law and to facilitate the movement of persons, property, and inheritance rights . Therefore, interpreting the mere presence of a foreign element as rendering a will objectionable would contradict the very structure of the system.

The practical consequence is important: anyone who wants to challenge cannot rely on a generic suspicion, nor on the intuition that "something foreign" must be legally weak.

It must identify a real and legally relevant reason : the testator's incapacity under the applicable law, a sufficient formal defect, an invalid choice of law, lack of proof of foreign law, a genuine violation of public policy, or the absence of documentary authenticity. Without one of these grounds, the claim is improperly filed from the outset.

The first question is not whether the will is fair, but what law governs it.

Before litigating, the decisive question is not whether the content of the will seems reasonable in light of the Spanish Civil Code, but which legal system actually regulates the succession.

In cross-border successions, the applicable law is usually determined by the habitual residence of the deceased and, in certain cases, by a valid professio iuris , that is, by a choice of the testator's national law to govern his entire succession.

This explains why so many arguments about challenging a will start from a flawed premise. The will is challenged as if the inheritance were necessarily subject to Spanish law, when it may be governed by a foreign law that allows for different substantive solutions.

This difference becomes especially noticeable in matters of forced heirship, inheritance institutions, or the scope of testamentary freedom.

It is incorrect to claim that an international will is contestable in Spain simply because it does not respect Spanish inheritance categories.

If the applicable law is different and that law supports the provision in question, the objection based exclusively on Spanish internal standards will not normally succeed. 

The unity of the succession reduces opportunistic challenges

Another major reason why not all international wills are contestable lies in the unitary model that inspires the European succession system.

The underlying idea is simple: a single law should govern the entire succession , avoiding fragmenting it according to the country where the assets are located or their nature.

This design does not eliminate conflicts, but it does make it more difficult to construct strategic challenges "on demand".

Under a fragmented approach, a disgruntled heir could try to challenge the validity of real estate in Spain under one law, personal property in another country under another, and the testator's capacity under a third legal framework. The system aims precisely to prevent this patchwork.

Not every obstacle is a nullity: sometimes the problem is evidentiary or documentary.

Here a distinction appears that, before going to trial, is decisive: the difference between substantive invalidity and difficulty of effectiveness in Spain.

Many controversies presented as "challenges" are, in reality, problems of proof of foreign law, legalization, apostille, sufficiency of the succession title or documentary adaptation to the Spanish system.

This is extremely important. If the defect is remediable, it may not be advisable to litigate for annulment, but rather to complete the documentation, better prove the foreign law, or correct the notarial and registry strategy.

The lack of proof of foreign law may prevent the will from having effects in Spain , but that does not necessarily mean that the will is invalid in itself.

That difference changes everything: it changes the course of action, the evidence, the financial risk, and even the client's expectations. Suing for annulment where there is only a lack of documentation is usually a costly mistake.

When is it worth considering an appeal?

The fact that not all international wills are contestable does not mean that none are. Rather, it means that challenging a will requires a methodical approach: verifying whether a genuine cross-border element exists; determining the applicable law; assessing whether an exception is warranted; and examining, if a choice of law is made, whether it is express or unequivocally implied by the testamentary disposition.

Only then does it make sense to analyze the specific causes. Among them, the testator's capacity plays a central role, but here too it's important to avoid automatic assumptions.

In general , it is not enough to prove a pathology or an illness: what is relevant is the state of the testator at the exact moment of granting.

Therefore, a challenge built solely on prior or subsequent diagnoses, without specific proof of the moment of testing, usually starts from a weakened position. 

The same applies to formal defects. The system does not favor destructive formalism. The testamentary form is a guarantee, yes, but not every minor non-compliance compromises the authenticity of the testator's wishes.

The principle of preserving the will carries significant weight in this area. 

Public order is not an open door to "Spanishize" every succession

One of the most frequently invoked and most misused arguments is that of Spanish public order. It is often presented as if a significant difference with Spanish law were sufficient to block the application of a foreign law.

However, public policy operates as a restrictive exception ; it is not a general clause to displace any foreign solution that inconveniences the interpreter.

This means, for example, that the mere absence of a legal share equivalent to the Spanish one or a less protective regulation of certain heirs does not automatically trigger the corrective of public order.

Turning every difference into an infringement would distort the international system of succession and empty the application of foreign law of its meaning.

Conclusion

Not all international wills are contestable because internationality , by itself, does not invalidate anything.

What it does is activate a preliminary technical analysis: whether there is a real cross-border element, what law governs the succession, whether there was a valid choice of law, whether the will meets the required material and formal requirements, and whether the problem detected is truly substantive or merely documentary. 

Before litigating, the useful question is not "this comes from abroad and therefore can be challenged?", but a much more precise one: "is there a serious legal cause, based on the applicable law, that justifies requesting the nullity or ineffectiveness?".

When that answer is unclear, the prudent course of action is not to sue, but to better understand the conflicting legal landscape. In international succession cases, this distinction separates sound legal challenges from procedural gambles.

RRYP Global, lawyers specializing in contesting international wills in Spain.