Short answer. Yes. When the owner of the principal thing acted in bad faith by incorporating your accessory without consent, you may choose between receiving its value or demanding its physical separation — even if separation destroys the principal — and you are also entitled to damages in either case.
What the law says
If the one who has acted in bad faith is the owner of the principal thing, the owner of the accessory thing shall have a right to choose between the former paying him its value or that the thing belonging to him be separated, even though for this purpose it be necessary to destroy the principal thing; and in both cases, furthermore, there shall be indemnity for damages.
Civil Code, Article 470 — Bad Faith in Adjunction. Read the full provision →
What the law gives you when the other owner acted in bad faith
Article 470 of the Civil Code draws a clear line between an owner who acted honestly and one who did not. When the owner of the principal thing made the incorporation without your consent and in bad faith, the law shifts the entire burden onto them. You are not left to absorb the loss simply because your item is now physically attached to something larger. Instead, you are given a genuine choice: demand the current value of your accessory, or demand its physical return — even if returning it means the principal thing is destroyed in the process.
Your two options and how to think about them
The first option — payment of value — is the practical choice when separation is technically possible but economically senseless, or when you simply want to be made whole in money. The second option — physical separation — is available even if the principal thing will be ruined. This is a deliberate consequence the law imposes on an owner who acted in bad faith: they cannot hide behind the fact that the things are now joined. Whichever option you choose, you are also entitled to indemnity for damages — costs, losses, and any other harm caused by the wrongful incorporation.
When the situation is reversed: you incorporated in bad faith
The same article covers the mirror situation. If you were the one who incorporated your accessory into another person's principal thing without consent and in bad faith, the outcome is starkly different: you lose the incorporated thing entirely, and you must still pay the principal owner for any damages suffered. There is no right to demand payment or separation when the bad faith is yours.
What if both parties knew and neither objected?
Article 470 also addresses a middle ground: if either owner made the incorporation with the knowledge and without the objection of the other, both parties are treated as though they acted in good faith. This matters because good-faith rules distribute the outcome more evenly — the accessory owner does not get the drastic remedy of demanding destruction of the principal. Whether objection was actually given, and when, becomes a key factual question if this defense is raised.