Section 23 of Republic Act No. 9165, which prohibits plea bargaining in all cases involving violations of the said Act, is unconstitutional because it contravenes the exclusive power of the Supreme Court to promulgate rules concerning pleading, practice, and procedure in all courts, as mandated by Section 5(5), Article VIII of the 1987 Constitution.

• The case arose within the context of the Philippine government's intensified campaign against illegal drugs, governed by Republic Act No. 9165.
• RA 9165 contained a specific provision, Section 23, that explicitly disallowed plea bargaining for any offense under the Act, diverging from the general availability of plea bargaining in other criminal cases under the Rules of Court.

• Petitioner Salvador A. Estipona, Jr. was charged with violation of Section 11, Article II of R.A. No. 9165 for possessing one sachet containing 0.084 grams of methamphetamine hydrochloride (shabu).
• On June 15, 2016, Estipona filed a "Motion to Allow the Accused to Enter into a Plea Bargaining Agreement," seeking to withdraw his initial not guilty plea and plead guilty to the lesser offense of violation of Section 12, Article II of R.A. No. 9165 (Possession of Equipment, Instrument, Apparatus and Other Paraphernalia for Dangerous Drugs).
• Estipona cited his status as a first-time offender and the minimal quantity of drugs seized as reasons for seeking rehabilitation through plea bargaining.
• The prosecution opposed the motion, citing Section 23 of R.A. No. 9165, which prohibits plea bargaining in drug cases.
• The Regional Trial Court (RTC), presided over by respondent Judge Frank E. Lobrigo, denied Estipona's motion in an Order dated July 12, 2016, upholding the prohibition in Section 23.
• The RTC acknowledged the argument that Section 23 might encroach on the Supreme Court's rule-making power but declined to declare it unconstitutional, citing "becoming modesty" and potential ramifications on pending drug cases.
• Estipona's motion for reconsideration was denied by the RTC on July 26, 2016.

• Section 23 of R.A. No. 9165 is unconstitutional because it violates the intent of the law (expressed in Sec. 2, par. 3) to rehabilitate offenders.
• Section 23 infringes upon the exclusive rule-making authority of the Supreme Court under Section 5(5), Article VIII of the 1987 Constitution, as plea bargaining is a rule of procedure.
• Section 23 violates the principle of separation of powers by allowing the legislative branch to dictate procedural rules, a power exclusively vested in the judiciary.
• Section 23 violates the constitutional right to equal protection of the laws, as it prohibits plea bargaining in drug cases while allowing it for other crimes, including heinous ones.
• The respondent RTC committed grave abuse of discretion amounting to lack or excess of jurisdiction when it refused to declare Section 23 unconstitutional despite recognizing its potential conflict with the Court's rule-making power.

• The Office of the Solicitor General (OSG), representing the People, argued the petition was procedurally defective for failing to implead Congress, attacking the law collaterally, and choosing the wrong remedy (should have been declaratory relief or certiorari before the RTC).
• The OSG contended that the requisites for judicial review were not met: petitioner lacked legal standing (no direct injury shown), there was no actual case or controversy, and the constitutionality of Section 23 was not the lis mota of the case.
• The OSG initially argued that the prohibition in Section 23 was justified by Congress' prerogative to choose which offenses allow plea bargaining.
• The RTC, in its Order, argued that while petitioner's points on encroachment might have merit, lower courts should exercise "becoming modesty" and refrain from declaring laws unconstitutional due to potential far-reaching consequences.

• Whether Section 23 of Republic Act No. 9165 is unconstitutional for being violative of the constitutional right to equal protection of the law.
• Whether Section 23 of Republic Act No. 9165 is unconstitutional as it encroached upon the power of the Supreme Court to promulgate rules of procedure under Section 5(5), Article VIII of the 1987 Constitution.
• Whether the Regional Trial Court committed grave abuse of discretion amounting to lack or excess of jurisdiction when it refused to declare Section 23 of Republic Act No. 9165 as unconstitutional.

• The Supreme Court granted the petition for certiorari and prohibition.
• The Court declared Section 23 of Republic Act No. 9165 unconstitutional for violating the Supreme Court's exclusive rule-making authority under the 1987 Constitution.
• The Court traced the history of its rule-making power, highlighting that the 1987 Constitution removed Congress's previous power to repeal, alter, or supplement procedural rules, making the Court's power in this area exclusive.
• The Court affirmed that plea bargaining is a rule of procedure, falling squarely within its constitutional mandate to promulgate rules concerning pleading, practice, and procedure.
• By prohibiting plea bargaining in drug cases, Section 23 of RA 9165 effectively amended the Rules of Court, specifically Rule 116, Section 2 and Rule 118, Section 1, which permit plea bargaining – an act the legislature has no authority to do.
• The Court classified plea bargaining rules as procedural using the test from Fabian v. Hon. Desierto, as they regulate the judicial process for enforcing rights and duties and do not diminish, increase, or modify substantive rights.
• The Court brushed aside the procedural objections raised by the OSG, citing the transcendental importance of the issue and the Court's power to suspend its rules in the interest of substantial justice.
• The Court explicitly declined to rule on the issue of whether Section 23 violates the equal protection clause, deeming it unnecessary given the finding of unconstitutionality based on the encroachment on its rule-making power.
• The finding of unconstitutionality implicitly addresses the issue of grave abuse of discretion, as the RTC's refusal to permit plea bargaining was based on an invalid provision.

• Rule-Making Power of the Supreme Court (1987 Constitution, Art. VIII, Sec. 5(5)): Defined as the Supreme Court's exclusive authority to promulgate rules concerning the protection and enforcement of constitutional rights, pleading, practice, and procedure in all courts. This power is no longer shared with Congress, which cannot repeal, alter, or supplement such rules. This doctrine was the basis for invalidating Sec. 23, RA 9165.
• Separation of Powers: Defined as the constitutional principle distributing governmental powers among the legislative, executive, and judicial branches, preventing encroachment by one branch upon the functions of another. Applied here to show that Congress (legislative) infringed upon the Judiciary's (Supreme Court) exclusive power over court procedure by enacting Sec. 23, RA 9165.
• Plea Bargaining as a Rule of Procedure: Defined plea bargaining as a process governed by the Rules of Court (specifically Rule 116, Sec. 2 and Rule 118, Sec. 1) whereby the accused and prosecution negotiate a mutually satisfactory disposition subject to court approval. The Court held it is procedural in nature and thus falls under its exclusive rule-making power.
• Substantive vs. Procedural Law Test (Fabian v. Hon. Desierto): Defined substantive law as that which creates, defines, and regulates rights, while procedural law prescribes the method of enforcing rights or obtaining redress. The test used is whether the rule regulates the judicial process for enforcing rights (procedural) or if it takes away a vested right or creates a new right (substantive). Applied to confirm plea bargaining rules are procedural.
• Transcendental Importance: Defined as a doctrine allowing the Court to disregard procedural barriers and technicalities to resolve constitutional issues of overriding public interest and far-reaching implications. Invoked by the Court to justify taking cognizance of the petition despite alleged procedural flaws raised by the OSG.
• Judicial Deference to Prosecutorial Discretion: Acknowledged the general principle that courts defer to the prosecutor's decision on whom to prosecute and the specific charge, as the prosecutor controls the prosecution. However, this discretion in accepting a plea bargain offer is subject to the rules established by the Court.
• Court's Discretion in Plea Bargaining: While initiated by the parties, the acceptance of a plea bargain ultimately rests on the sound discretion of the trial court, requiring consent from the prosecutor and the offended party (in applicable cases), and evaluation of evidence if the plea change occurs after prosecution rests.

• "In fine, the power to promulgate rules of pleading, practice and procedure is no longer shared by this Court with Congress, more so with the Executive."
• "The separation of powers among the three co-equal branches of our government has erected an impregnable wall that keeps the power to promulgate rules of pleading, practice and procedure within the sole province of this Court."
• "Plea bargaining is a rule of procedure."
• "In determining whether a rule prescribed by the Supreme Court... abridges, enlarges, or modifies any substantive right, the test is whether the rule really regulates procedure... if it operates as a means of implementing an existing right then the rule deals merely with procedure."
• "Section 23 of Republic Act No. 9165 is declared unconstitutional for being contrary to the rule-making authority of the Supreme Court under Section 5(5), Article VIII of the 1987 Constitution."

• Echegaray v. Secretary of Justice (1999): Cited extensively for tracing the history and evolution of the Supreme Court's rule-making power, emphasizing its expansion and exclusivity under the 1987 Constitution.
• Carpio-Morales v. Court of Appeals (Sixth Division) (2015): Cited to reinforce the exclusive nature of the Supreme Court's rule-making power under the 1987 Constitution, contrasting it with Congress's power over court jurisdiction, and affirming the deletion of Congress's power to amend procedural rules. Also cited regarding the unconstitutionality of Sec. 14 of RA 6770 (Ombudsman Act) for contravening Rule 58.
• Fabian v. Desierto (1998): Cited for establishing the test to determine whether a rule is substantive or procedural. Also cited as an instance where the Court invalidated a statutory provision (Sec. 27, RA 6770) for conflicting with procedural rules (Rule 43 vs Rule 45).
• People v. Lacson (2003): Cited as an example where a procedural rule (Rule 117, Sec. 8 on provisional dismissal time-bar) was upheld against claims that it diminished substantive rights, illustrating the Court's balancing of interests in procedural rule-making.
• Jaylo, et al. v. Sandiganbayan, et al. (2015): Cited as another example where a procedural rule (Rule 120, Sec. 6 on forfeiture of remedies for non-appearance at promulgation) was upheld as merely regulating the implementation of existing rights, not diminishing them.
• People v. Villarama, Jr. (1992): Cited for the definition of plea bargaining in Philippine jurisdiction and for establishing that the State is the offended party in drug cases, requiring the prosecutor's consent for a plea bargain.
• In re: Cunanan (1954): Cited historically to show the Court asserting its power over admission to the bar against legislative encroachment even under the 1935 Constitution's shared power framework.
• Brady v. United States (1970), Santobello v. New York (1971), Blackledge v. Allison (1977): US Supreme Court cases cited to illustrate the rationale, benefits (speed, economy, finality, rehabilitation prospects), and importance of plea bargaining in the administration of justice.
• Weatherford v. Bursey (1977): Cited for the principle that a defendant has no constitutional right to plea bargain; it is not mandatory for the prosecutor to offer or accept one.
• Daan v. Hon. Sandiganbayan (2008): Cited regarding the discretionary nature ('may') of the court's power to allow plea bargaining and the need for the court's ruling to be based on evidence.

• 1987 Constitution, Article VIII, Section 5(5): The core provision granting the Supreme Court exclusive power to promulgate rules of procedure.
• Republic Act No. 9165 (Comprehensive Dangerous Drugs Act of 2002):
  • Section 2: Declaration of Policy (including rehabilitation).
  • Section 11: Possession of Dangerous Drugs (the original charge against petitioner).
  • Section 12: Possession of Equipment, Instrument, Apparatus and Other Paraphernalia (the lesser offense petitioner sought to plead guilty to).
  • Section 23: Plea-Bargaining Provision (the provision declared unconstitutional).
• Rules of Court:
  • Rule 116, Section 2 (Arraignment and Plea): Governs plea of guilty to a lesser offense.
  • Rule 118, Section 1 (Pre-trial): Mandates consideration of plea bargaining during pre-trial.
  • Rule 117, Section 8 (Provisional Dismissal): Referenced in the Lacson case discussion.
  • Rule 120, Section 6 (Judgment): Referenced in the Jaylo case discussion.
  • Rule 141 (Legal Fees): Referenced in cases involving exemption from legal fees (RE: GSIS Exemption, BAMARVEMPCO, RE: NPC Exemption).
  • Rule 58 (Preliminary Injunction): Referenced in the Carpio-Morales discussion on RA 6770.
  • Rule 43 & Rule 45 (Appeals): Referenced in the Fabian case discussion.
  • Rule 14 (Summons): Referenced in the Cathay Metal case discussion.
• Republic Act No. 8493 (Speedy Trial Act of 1998): Mentioned as its Section 2 adopted the Rules of Court provision requiring consideration of plea bargaining during pre-trial.
• Republic Act No. 6425 (Dangerous Drugs Act of 1972): Mentioned as its Section 20-A (as amended by RA 7659) previously prohibited plea bargaining only when the penalty was reclusion perpetua to death.
• Republic Act No. 7659 (Death Penalty Law): Mentioned as amending RA 6425 regarding plea bargaining.
• Republic Act No. 6770 (Ombudsman Act of 1989): Sections 14 and 27 were mentioned as having been declared unconstitutional in Carpio-Morales and Fabian for infringing on the Rules of Court.

• Justice Marvic M.V.F. Leonen — Concurred with the ponencia, adding that Section 23 of R.A. 9165 is unconstitutional not only for contravening the Court's rule-making power but also because it constitutes a "cruel, degrading, [and] inhuman" punishment under Article III, Section 19 of the Constitution. He argued that prohibiting plea bargaining prevents rehabilitation (a declared policy of R.A. 9165) and has a disproportionately harsh impact, especially on the poor caught with minuscule amounts of drugs who face mandatory life imprisonment for selling, hindering their reintegration into society. He reserved judgment on whether life imprisonment itself is cruel for minor drug trading.