Short answer. It is punishable even without the coup. Article 136 punishes the mere conspiracy or proposal to commit a coup d'etat with prisión mayor in its minimum period and a fine of up to one million pesos, even if the coup never happens. The fine amount comes from Republic Act No. 10951.
What the law says
The conspiracy and proposal to commit coup d’etat shall be punished by prisión mayor in its minimum period and a fine which shall not exceed One million pesos (₱1,000,000).
Revised Penal Code, Article 136 — Conspiracy To Commit Rebellion. Read the full provision →
The plot itself is punished
For the gravest offenses against the State, the law reaches the planning stage. Article 136 provides that the conspiracy and proposal to commit coup d'etat shall be punished by prisión mayor in its minimum period and a fine which shall not exceed One million pesos (₱1,000,000). So people who agree to carry out a coup, or who propose one, can be prosecuted for the conspiracy or proposal alone, even if the coup is never actually attempted or carried out. The State does not have to wait for the seizure of power to begin before acting against those who have plotted it.
The penalty for a coup plot
Conspiracy and proposal to commit a coup d'etat carry prisión mayor in its minimum period, a significant term of imprisonment, along with a fine that may reach one million pesos. The peso figure reflects Republic Act No. 10951, which revised the Code's monetary penalties in 2017, so the current ceiling comes from that law. Punishing the plot at this level signals that agreeing or proposing to overthrow or seize power from the duly constituted authorities is itself a grave crime, quite apart from any later acts of execution.
Rebellion and insurrection on a separate scale
The same article addresses related offenses on a lighter footing. Conspiracy and proposal to commit rebellion or insurrection are punished respectively by prisión correccional in its maximum period with a fine not exceeding one million pesos, and by prisión correccional in its medium period with a fine not exceeding four hundred thousand pesos. So while the law punishes the plotting of a coup, of rebellion, and of insurrection alike, it calibrates the penalties differently among them, with the coup plot drawing the heavier prisión mayor. All these fines derive from the amounts set by Republic Act No. 10951.
Why punish the agreement
Reaching conspiracy and proposal lets the law intervene before an assault on the government can unfold, when intervention can still prevent serious harm. A coup, rebellion, or insurrection threatens the constitutional order itself, so the State treats an agreement or proposal to commit one as dangerous enough to punish on its own. This is why Article 136 does not require the coup to have occurred: the danger lies in the plot, and stopping it early, by punishing those who conspire or propose, is the point of the provision.