Short answer. Yes. Article 2051 provides that a guaranty may be constituted not only in favour of the principal debtor but also in favour of another guarantor. You can guarantee a fellow guarantor — and remarkably, you may do so with his consent, without his knowledge, or even over his objection.
What the law says
A guaranty may be conventional, legal or judicial, gratuitous, or by onerous title.
Civil Code, Article 2051 — Kinds of Guaranty. Read the full provision →
What the law says
not only in favor of the principal debtor, but also in favor of the other guarantor
Civil Code, Article 2051 — Kinds of Guaranty. Read the full provision →
What the law says
with the latter's consent, or without his knowledge, or even over his objection
Civil Code, Article 2051 — Kinds of Guaranty. Read the full provision →
The kinds of guaranty the article lists
Before it reaches your question, the article maps the terrain. A guaranty may be conventional, legal or judicial, gratuitous, or by onerous title. A guaranty can arise from the parties' agreement (conventional), from a requirement of law (legal), or from a court's order in a proceeding (judicial); and it may be given for free (gratuitous) or for a price (by onerous title). These categories describe how a guaranty comes into being and whether the guarantor is paid, and they matter because they affect how strictly the guarantor's undertaking is read and what he can expect in return for shouldering another's risk.
A guaranty can back another guarantor
Then the article answers directly: a guaranty may be constituted not only in favor of the principal debtor, but also in favor of the other guarantor. This is the sub-guaranty. Instead of backing the debtor, you back a guarantor — undertaking that if the guarantor is called on and cannot make good, you will. It is a guaranty of a guaranty, one step further removed from the original debt. The law expressly permits it, so a person worried that a particular guarantor may not hold up can be given his own guarantor, adding a further layer of security behind the primary one.
Why the guaranteed guarantor's consent is not needed
The striking part is how little the guaranteed guarantor's wishes count. The article allows the sub-guaranty to be set up with the latter's consent, or without his knowledge, or even over his objection. This makes sense once you see who benefits and who is burdened. A guaranty imposes an obligation on the guarantor for someone else's account; it does not take anything from the person guaranteed. Standing behind a guarantor only improves that guarantor's position — there is now someone to share or absorb his exposure — so his agreement is not needed. He cannot be worse off for having a backer, which is why even his objection does not prevent it.
What this means practically
In practice this means a creditor, or anyone relying on a guarantor, can strengthen a chain of security without negotiating with everyone in it. A sub-guarantor takes on a real obligation, though a contingent and secondary one: he answers only if the guarantor he backs is liable and defaults. Anyone asked to act as a sub-guarantor should therefore understand exactly whose default triggers his liability — the guarantor's, not merely the debtor's — and read the instrument accordingly. And a guarantor cannot block someone from guaranteeing him, because the arrangement adds to his protection rather than his burden.