Short answer. Generally, no. The Family Code prohibits renouncing or transferring parental authority by private contract. Parental authority is a legal status attached to parenthood, not a right you can give away by agreement. Only the situations expressly authorized by law allow it to be transferred.
What the law says
Parental authority and responsibility may not be renounced or transferred except in the cases authorized by law.
Family Code, Article 210 — Parental Authority Cannot Be Renounced or Transferred. Read the full provision →
The rule: you cannot contract away parental authority
Article 210 of the Family Code states plainly: Parental authority and responsibility may not be renounced or transferred except in the cases authorized by law. This means a private agreement between parents and grandparents — or between parents and anyone else — purporting to hand over parental authority has no legal effect. Parental authority is not a tradeable right. It comes with parenthood and remains with the parent unless the law itself provides a mechanism for transferring or suspending it.
Why the law forbids private transfers
The prohibition exists to protect the child. Parental authority is not merely a right — it is inseparably tied to parental responsibility. Allowing parents to sign it away by contract would let them escape the duties that come with it: care, education, support, representation. A grandparent who receives authority by contract has no enforceable legal basis for it, and the original parent remains legally responsible. The child would be in an ambiguous situation, with the real caretaker having no recognized legal standing and the legal parent having escaped accountability through a piece of paper.
What can legally happen
The Family Code does recognize situations where parental authority moves from a parent to someone else — but only through channels the law itself authorizes. Suspension or deprivation of parental authority requires a court proceeding and a finding based on recognized grounds. Substitute parental authority over the child in case of a parent's absence is governed by a specific order of priority set by law. Adoption extinguishes the biological parent's authority and vests it in the adoptive parent, again through a court process. None of these happen by signing a document.
A deed of authority is not the same as legal authority
Families sometimes execute a document authorizing a grandparent or relative to act on the child's behalf for school enrollments, medical decisions, or travel. Such documents may be practically useful for dealing with institutions — but they do not transfer parental authority in the legal sense. The parent retains all the rights and responsibilities of parenthood. If a real transfer of authority is what the family needs — for example, because a parent is going abroad for an extended period — the proper legal step is to look into guardianship or adoption proceedings, not a private contract.