Legislative reapportionment, which involves the creation or realignment of legislative districts for purposes of representation in the legislature, is fundamentally different from the creation, division, merger, abolition, or substantial alteration of boundaries of a local government unit, and thus does not require the conduct of a plebiscite for its validity.

On October 10, 2006, then Congressman Constantino G. Jaraula of Cagayan de Oro City filed House Bill No. 5859, "An Act Providing for the Apportionment of the Lone Legislative District of the City of Cagayan De Oro." This bill was subsequently enacted into Republic Act No. 9371, which increased the city's legislative districts from one to two. The law mandated that for the May 2007 elections, voters in Cagayan de Oro would be classified as belonging to either the first or second legislative district based on their residence, with each district electing its own representative to Congress and eight members to the Sangguniang Panglungsod.

• Republic Act No. 9371, an act apportioning the lone legislative district of Cagayan de Oro City, increased the city's legislative districts from one to two.
• Section 1 of R.A. No. 9371 delineated the specific barangays that would comprise the first legislative district and the second legislative district.
• On March 13, 2007, the Commission on Elections (COMELEC) en Banc promulgated Resolution No. 7837, implementing R.A. No. 9371 for the upcoming May 14, 2007 National and Local Elections.
• Petitioner Rogelio Bagabuyo filed a petition for certiorari, prohibition, and mandamus seeking to nullify R.A. No. 9371 and COMELEC Resolution No. 7837 on constitutional grounds, primarily arguing that a plebiscite was required.
• The Supreme Court did not grant the petitioner's prayer for a temporary restraining order or writ of preliminary injunction, and thus the May 14, 2007 elections proceeded as scheduled under R.A. No. 9371 and Resolution No. 7837.
• According to the August 2007 census of the National Statistics Office, the first district of Cagayan de Oro had a total population of 254,644, while the second district had 299,322 residents.

• The COMELEC cannot implement R.A. No. 9371 without providing rules, regulations, and guidelines for a plebiscite, which is indispensable for the division or conversion of a local government unit.
• R.A. No. 9371's reapportionment of Cagayan de Oro City falls within the meaning of creation, division, merger, abolition, or substantial alteration of boundaries of cities under Section 10, Article X of the Constitution, thus requiring a plebiscite.
• The reapportionment results in a material change in the political and economic rights of the local government unit and its people.
• A voter's sovereign power to elect the entire city's Congressman was arbitrarily reduced by half, as the law only allowed voting for a representative in the designated district.
• A voter was arbitrarily denied the right to elect the Congressman and members of the city council for the other legislative district.
• Government funds were allegedly illegally disbursed without prior approval by the sovereign electorate of Cagayan de Oro City.
• R.A. No. 9371 violates the principle of equality of representation due to the disparity in the number of registered voters between the two newly created districts and their differing rural-urban compositions.

• The petitioner violated the principle of hierarchy of courts by directly filing the petition with the Supreme Court, as the Regional Trial Court has concurrent jurisdiction over cases assailing a statute's constitutionality.
• R.A. No. 9371 merely increased the representation of Cagayan de Oro City in the House of Representatives and Sangguniang Panglungsod, pursuant to Section 5, Article VI of the 1987 Constitution.
• The criteria established under Section 10, Article X of the 1987 Constitution, including the plebiscite requirement, apply only when there is a creation, division, merger, abolition, or substantial alteration of boundaries of a province, city, municipality, or barangay.
• No such creation, division, merger, abolition, or alteration of boundaries of Cagayan de Oro City as a local government unit took place under R.A. No. 9371.
• R.A. No. 9371 did not bring about any change in Cagayan de Oro's territory, population classification, or income classification; hence, no plebiscite is required.

• Whether the petitioner violated the hierarchy of courts rule, and if so, whether the petition should be dismissed on this ground.
• Whether R.A. No. 9371 merely provides for the legislative reapportionment of Cagayan de Oro City, or whether it involves the division and conversion of a local government unit requiring a plebiscite.
• Whether R.A. No. 9371 violates the equality of representation doctrine.

• The Supreme Court found the petition to be an exception to the principle of hierarchy of courts because it assailed the validity of a legislative enactment (R.A. No. 9371) and a COMELEC en banc resolution (No. 7837), which falls under Rule 64 of the Rules of Court requiring review by the Supreme Court via a Rule 65 petition for certiorari.
• R.A. No. 9371 is purely a legislative reapportionment law, distinct from the division of a local government unit; legislative apportionment under Article VI, Section 5 of the Constitution does not require a plebiscite, unlike the creation, division, merger, abolition, or substantial alteration of boundaries of local government units under Article X, Section 10 of the Constitution.
• The Court explained that legislative districts are representative units for electing members of the legislature and are not corporate political subdivisions with their own governance structures or legal personality that would necessitate a plebiscite for their alteration.
• R.A. No. 9371 did not divide Cagayan de Oro City as a political and corporate entity; the city remains a single unit, its territory intact, with only an additional legislative district for representation purposes.
• The increase in Sangguniang Panglunsod members is a consequence of R.A. No. 6636, not R.A. No. 9371 directly, and also does not constitute a division of the city as an LGU.
• The petitioner's argument on the violation of equality of representation based on disparate numbers of registered voters and rural/urban composition was dismissed; the constitutional basis for districting is the number of inhabitants, not registered voters, and the Constitution does not demand mathematical exactitude in population size between districts, only that they be, as far as practicable, continuous, compact, and adjacent. Differences in development levels are policy matters for the legislature, not constitutional infirmities, absent grave abuse of discretion.
• The petition was dismissed for lack of merit.

• Principle of Hierarchy of Courts — This principle dictates that where courts have concurrent jurisdiction, litigants must first seek relief from the lower court. The Supreme Court held that the case was an exception because it involved a challenge to the validity of a legislative enactment and a COMELEC en banc resolution, matters of significant public interest warranting direct recourse.
• Legislative Apportionment vs. Division of Local Government Units — Legislative apportionment under Article VI, Section 5 of the Constitution refers to the determination and allocation of legislative seats and the drawing of district lines for representation, while the division of local government units under Article X, Section 10 refers to the creation, division, merger, abolition, or substantial alteration of the boundaries of provinces, cities, municipalities, or barangays as corporate and political entities. The Court emphasized that R.A. No. 9371 was an act of legislative apportionment, not a division of Cagayan de Oro City as an LGU, and thus did not require a plebiscite.
• Plebiscite Requirement for Local Government Unit Changes — Article X, Section 10 of the Constitution and the Local Government Code mandate a plebiscite for any creation, division, merger, abolition, or substantial alteration of boundaries of a local government unit. This doctrine was deemed inapplicable because R.A. No. 9371 only involved legislative reapportionment.
• Equality of Representation — This principle, rooted in Article VI, Section 5 of the Constitution, requires that legislative districts be apportioned based on the number of inhabitants and on the basis of a uniform and progressive ratio, and comprise, as far as practicable, continuous, compact, and adjacent territory. The Court ruled that mathematical exactitude in population numbers between districts is not required, and disparities are permissible as long as constitutional standards are generally met and there is no grave abuse of discretion by the legislature. The basis for districting is inhabitants, not registered voters.

• "Historically and by its intrinsic nature, a legislative apportionment does not mean, and does not even imply, a division of a local government unit where the apportionment takes place. Thus, the plebiscite requirement that applies to the division of a province, city, municipality or barangay under the Local Government Code should not apply to and be a requisite for the validity of a legislative apportionment or reapportionment."
• "The Constitution, however, does not require mathematical exactitude or rigid equality as a standard in gauging equality of representation."
• "In the absence of any grave abuse of discretion or violation of the established legal parameters, this Court cannot intrude into the wisdom of these policies."

• Del Mar v. PAGCOR — Cited by petitioner to argue that the Court may take cognizance of a petition if compelling reasons or the nature and importance of the issues raised warrant immediate exercise of its jurisdiction, as an exception to the hierarchy of courts.
• Tobias v. Abalos — Referenced as a key precedent confirming that no plebiscite is needed in a legislative reapportionment, distinguishing it from the conversion of a municipality into a highly urbanized city which does require a plebiscite.
• Macias v. COMELEC — Cited for jurisprudentially acknowledging the American roots of the Philippines' apportionment provision and for ruling that inequality of representation is a justiciable issue.
• Montejo v. COMELEC — Cited as reiterating the ruling in Macias that inequality of representation is a justiciable issue.
• Herrera v. COMELEC — Cited to establish that the basis for legislative districting is the number of inhabitants, not the number of registered voters.

• Constitution, Article VI, Section 5 — Lays down the rules on legislative apportionment, including the composition of the House of Representatives, the criteria for legislative districts (population, contiguity, compactness, adjacency), and the mandate for Congress to make reapportionments. This was the primary constitutional basis for upholding R.A. No. 9371.
• Constitution, Article X, Section 10 — Governs the creation, division, merger, abolition, or substantial alteration of boundaries of local government units, requiring compliance with criteria in the Local Government Code and approval by plebiscite. The Court found this provision inapplicable to legislative reapportionment.
• Constitution, Article VIII, Section 5(1) — Grants the Supreme Court original jurisdiction over petitions for certiorari, prohibition, mandamus, quo warranto, and habeas corpus. Invoked as the basis for the Court's jurisdiction over the petition.
• Rules of Court, Rule 64 — Governs review of judgments and final orders or resolutions of the Commission on Elections and the Commission on Audit. Cited as a reason for the Supreme Court taking direct cognizance of the case.
• Rules of Court, Rule 65 — Pertains to petitions for certiorari, prohibition, and mandamus. The petition was filed under this rule.
• Republic Act No. 9371 — The law being challenged, which apportioned the lone legislative district of Cagayan de Oro City into two districts. The Court upheld its constitutionality.
• COMELEC Resolution No. 7837 — The resolution implementing R.A. No. 9371, also challenged by the petitioner. Its validity was upheld as a consequence of upholding R.A. No. 9371.
• Republic Act No. 6636, Section 3 — Provides for the number of Sangguniang Panglunsod councilors in cities with more than one representative district. Cited to explain the increase in councilors in Cagayan de Oro City.
• Local Government Code (R.A. No. 7160) — Referenced for establishing criteria (income, population, land area) for the creation, division, etc., of local government units, and for the plebiscite requirement.