Short answer. Yes. Article 921 of the Civil Code lists giving cause for legal separation as a ground for disinheritance. The law does not require you to have filed or won a legal separation case first. What matters is that the conduct occurred — not that it was adjudicated in a separate proceeding.
What the law says
When the spouse has given cause for legal separation;
Civil Code, Article 921 — Grounds to Disinherit a Spouse. Read the full provision →
Giving cause for legal separation is itself the ground
Article 921 of the Civil Code lists six grounds for disinheriting a spouse, and the fourth is: when the spouse has given cause for legal separation. The phrasing is significant — it refers to the spouse's conduct, not to the existence of a legal separation decree. You do not need to have filed for legal separation, let alone obtained a final judgment. If your spouse did something that constitutes a ground for legal separation — such as physical violence, moral pressure, infidelity, sexual perversion, abandonment, or drug addiction — that conduct itself is sufficient to invoke this disinheritance ground.
What constitutes cause for legal separation
The Family Code enumerates the grounds for legal separation. These include repeated physical violence or grossly abusive conduct against the petitioner, a child, or a common child; physical violence or moral pressure to compel the petitioner to change religious or political affiliation; drug addiction or habitual alcoholism; lesbianism or homosexuality; contracting a bigamous marriage; sexual infidelity or perversion; attempt of the spouse to corrupt or induce the petitioner, a common child, or their child to engage in prostitution; and abandonment without justifiable cause for more than one year. If your spouse did any of these things, you have the conduct the law requires.
Proving the conduct in the will or in probate
Because no court has already adjudicated the legal separation, the burden of establishing that the conduct occurred falls on those who uphold the will in probate. The disinheritance must be stated in the will, with the reason expressed. During probate or any challenge, the heirs who support the will would present evidence of the spouse's conduct — testimony, records, documentation — to show the ground is real. This is why it is important to document the spouse's behavior: messages, police reports, medical records of injuries, records of other evidence of the conduct that gave legal separation cause.
Planning the disinheritance properly
Write the disinheritance into a valid will using explicit language that identifies the ground. Vague references to marital difficulties are not enough — the will should state specifically that your spouse gave cause for legal separation and describe, in general terms, the nature of that conduct. Pair the will with a personal written account kept separately that describes what happened and when. If witnesses observed the conduct, keep their names. The disinheritance holds if the evidence supports the ground at probate. Consulting a lawyer before executing the will gives you the best chance of making the disinheritance legally secure.