Short answer. No. Article 438 of the Civil Code gives a chance finder of hidden treasure on someone else's land a one-half share, but it expressly excludes trespassers: if the finder is a trespasser, he shall not be entitled to any share of the treasure. Trespassing on the land forfeits any claim to a portion of what is found there.
What the law says
If the finder is a trespasser, he shall not be entitled to any share of the treasure.
Civil Code, Article 438 — Who Owns Hidden Treasure. Read the full provision →
The baseline: treasure belongs to the landowner
Article 438 starts from a simple default: hidden treasure belongs to the owner of the land, building, or other property on which it is found. Ownership of the treasure follows ownership of the property, not the person who happens to dig it up. Everything else in the article — the finder's share, the trespasser exception — is a modification of that starting rule, not a replacement for it.
The one-half share only exists for a lawful chance finder
The article does create an exception in the finder's favor: when the discovery is made on the property of another, or of the State or any of its subdivisions, and by chance, one-half thereof shall be allowed to the finder. Two conditions have to be met for that half-share to arise — the treasure has to be found on someone else's property, and the discovery has to be by chance. Both conditions describe someone who has a lawful reason to be where they are, stumbling on the treasure incidentally rather than as a trespasser hunting for it.
Trespassing removes the share entirely
Article 438 addresses the trespasser scenario directly and without ambiguity: if the finder is a trespasser, he shall not be entitled to any share of the treasure. This is not a reduced share or a share subject to conditions — it is a complete exclusion. Being on the land without a lawful right to be there when the discovery is made is enough, under this article, to forfeit any claim to what would otherwise have been a one-half portion for a chance finder.
A separate rule for items of scientific or artistic interest
Article 438 adds one more layer: if the things found be of interest to science or the arts, the State may acquire them at their just price, which shall be divided in conformity with the rule stated. That option belongs to the State, not the finder, and the division it describes still follows the same rule the article already set out — meaning a trespasser gains nothing from this provision either, since the underlying entitlement it distributes is the one already denied to them.