Short answer. Yes, but only in the same court proceeding and only if one of the law's specific triggering events applies — such as reconciliation after a year's factual separation, the absentee spouse reappearing, or parental authority being restored. You cannot revive the old regime simply because you both now prefer it.
What the law says
The spouses may, in the same proceedings where separation of property was decreed, file a motion in court for a decree reviving the property regime that existed between them before the separation of property
Family Code, Article 141 — Reviving the Former Property Regime. Read the full provision →
Reviving the old regime is a motion, not a fresh case
You do not have to start an entirely new case to bring back your former property regime. The law lets spouses file a motion in court for a decree reviving the property regime that existed between them before the separation of property, and specifies that this motion is filed "in the same proceedings where separation of property was decreed." The revival is treated as a continuation of that same case, not a separate action you have to initiate from scratch.
It only works if one of seven specific triggers applies
The right to revive is not open-ended. It is available only "in any of the following instances" the article lists: civil interdiction ending, the reappearance of an absentee spouse, the court authorizing resumption of administration after being satisfied the spouse will not abuse it again, a spouse who left the conjugal home without a legal separation decree resuming common life, parental authority being judicially restored, spouses who separated in fact for at least a year reconciling and resuming common life, or — where the separation followed a joint petition to voluntarily dissolve the property regime — the spouses simply agreeing to revive it. Which of these applies to you determines whether the motion has any legal footing at all.
Reviving through joint agreement comes with a permanent trade-off
The last of the seven grounds is different from the rest: where the property regime was dissolved on the spouses' own joint petition and they now agree to revive it, the article adds a firm consequence — "No voluntary separation of property may thereafter be granted." Once you use this path to revive the regime, that same couple loses access to a future voluntary separation of property. It is meant to be a one-time reset, not a door you can walk back through.
The revival itself follows a separate article's procedure
This article does not spell out every procedural detail of how the revival is carried out once granted; it states that "the revival of the former property regime shall be governed by Article 67" of the same code. That cross-reference matters because it means the mechanics of putting the old regime back into effect are not found here — they sit in a separate provision, and both articles need to be read together before assuming what happens next.