The selection of the Senate Minority Leader is an internal matter of the Senate, and courts will not interfere with such internal workings unless a clear violation of the Constitution, laws, or the Senate's own rules, or grave abuse of discretion amounting to lack or excess of jurisdiction, is demonstrated.

The case arose from the organization of the Eleventh Congress of the Philippines in July 1998. Following the election of Senator Marcelo B. Fernan as Senate President, a dispute emerged regarding who should be recognized as the Senate Minority Leader. Senator Tatad, who lost the bid for Senate President, claimed the position, supported by Senator Santiago. Simultaneously, a group of seven senators belonging to the Lakas-NUCD-UMDP party, also a minority bloc, elected Senator Teofisto T. Guingona Jr. as their choice for Minority Leader. Senate President Fernan eventually recognized Senator Guingona.

• On July 27, 1998, the Senate convened for the first regular session of the Eleventh Congress. Senator Marcelo B. Fernan was elected Senate President with 20 votes, defeating Senator Francisco S. Tatad who received 2 votes (from himself and Senator Santiago).
• Senator Tatad then manifested that, with Senator Santiago's agreement, he was assuming the position of Minority Leader, arguing that those who voted for the losing nominee for Senate President constituted the "minority."
• Senator Juan M. Flavier manifested that the seven senators belonging to the Lakas-NUCD-UMDP party, also a minority group, had chosen Senator Teofisto T. Guingona Jr. as the Minority Leader.
• After debates and a caucus failed to resolve the issue, on July 30, 1998, the Majority Leader informed the Senate that he received a letter from the seven Lakas-NUCD-UMDP senators stating they had elected Senator Guingona as Minority Leader.
• Consequently, Senate President Fernan formally recognized Senator Guingona as the Minority Leader of the Senate.
• Senators Santiago and Tatad filed a petition for quo warranto, alleging Senator Guingona was usurping the office of Senate Minority Leader.

• The Court has jurisdiction to interpret the constitutional provision regarding the election of the Senate President (Art. VI, Sec. 16(1)) to determine the concepts of "majority" and "minority" and who may elect a minority leader.
• The "majority" comprises senators who voted for the winning Senate President and accepted committee chairmanships; the "minority" consists of those who voted for the losing nominee and accepted no chairmanships.
• Respondent Guingona cannot be the legitimate minority leader because he voted for Respondent Fernan as Senate President.
• Members of Lakas-NUCD-UMDP cannot choose the minority leader as they did not belong to the "minority" having voted for Fernan and accepted committee chairmanships.
• Respondent Fernan acted with grave abuse of discretion in recognizing Respondent Guingona as minority leader.

• The issue of who is the lawful Senate Minority Leader is an internal matter of the Senate, beyond the Court's jurisdiction due to the principle of separation of powers.
• No constitutional issue is involved as the Constitution does not provide for the office of a minority leader in the Senate; the legislature has full discretion to provide for such office and determine the selection procedure.
• The case of Avelino v. Cuenco is inapplicable as there is no question involving an interpretation of the Constitution, laws, or Senate Rules, nor peculiar circumstances impelling Court intervention.
• There is no legislative practice supporting the theory that a senator voting for the winning Senate President is precluded from becoming the minority leader.
• Respondent Guingona was duly chosen by the Lakas-NUCD-UMDP, a minority party in the Senate, and subsequently recognized by the Senate President.

• Does the Court have jurisdiction over the petition?
• Was there an actual violation of the Constitution in the recognition of Respondent Guingona as Senate Minority Leader?
• Was Respondent Guingona usurping, unlawfully holding, and exercising the position of Senate Minority Leader?
• Did Respondent Fernan act with grave abuse of discretion in recognizing Respondent Guingona as the Minority Leader?

• Yes, the Court has jurisdiction over the petition because petitioners alleged a violation of the Constitution and grave abuse of discretion, bringing the matter within the Court's power of judicial review. Jurisdiction is determined by the allegations in the petition.
• No, there was no violation of the Constitution. Article VI, Section 16(1) only mandates that the Senate President be elected by a majority vote of all members; it does not define "majority" or "minority" in the context of other leadership positions, nor does it state that those who do not vote for the winning Senate President automatically constitute the minority entitled to elect the minority leader.
• No, Respondent Guingona was not usurping the office. The method of choosing other officers, like the Minority Leader, is a derivative of the Senate's prerogative under Article VI, Section 16(1) ("Each House shall choose such other officers as it may deem necessary") and is to be prescribed by the Senate itself. The Senate Rules do not provide for the positions of majority and minority leaders or the manner of their selection. Absent constitutional or statutory guidelines, or specific Senate rules, the Court cannot determine the legality of the acts of the Senate concerning this internal matter. Petitioners failed to show a clear and indubitable franchise to the office of Senate Minority Leader for Senator Tatad.
• No, Respondent Fernan did not act with grave abuse of discretion. He recognized Senator Guingona, who belonged to a minority party (Lakas-NUCD-UMDP) and was unanimously chosen by its members, only after Senate sessions and a caucus where both sides articulated their standpoints. There was no capricious or whimsical exercise of judgment.

• Separation of Powers — This principle ordains that each of the three great branches of government has exclusive cognizance of and is supreme in matters falling within its own constitutionally allocated sphere. The Court applied this by stating it cannot pry into the internal workings of the Senate, such as the selection of its Minority Leader, unless there is a clear constitutional or legal violation or grave abuse of discretion, as this is a matter within the Senate's competence.
• Judicial Review (Expanded Power under the 1987 Constitution) — Judicial power includes the duty of the courts to settle actual controversies involving legally demandable and enforceable rights and to determine whether there has been grave abuse of discretion amounting to lack or excess of jurisdiction on the part of any branch or instrumentality of the Government (Art. VIII, Sec. 1). The Court invoked this to assert its jurisdiction based on petitioners' allegations of constitutional violation and grave abuse of discretion, even if the matter pertained to a coequal branch.
• Political Question Doctrine — Refers to questions which, under the Constitution, are to be decided by the people in their sovereign capacity, or in regard to which full discretionary authority has been delegated to the legislative or executive branch. While traditionally limiting judicial intervention, the Court noted that the 1987 Constitution expanded judicial power to determine grave abuse of discretion, thereby narrowing the scope of non-justiciable political questions. However, the Court ultimately found the specific issue of choosing a minority leader, absent clear constitutional/legal breach, to be within the Senate's discretionary authority.
• Quo Warranto — A legal proceeding to determine the right or title to a contested public office and to oust the holder from its enjoyment. It requires the petitioner to show a clear right to the office. The Court found petitioners failed to establish a clear and indubitable franchise for Senator Tatad to the office of Senate Minority Leader.
• Grave Abuse of Discretion — Such capricious or whimsical exercise of judgment as is equivalent to lack of jurisdiction; an abuse of discretion so patent and gross as to amount to an evasion of positive duty or a virtual refusal to perform a duty enjoined by law, or to act at all in contemplation of law, as where the power is exercised in an arbitrary and despotic manner by reason of passion and hostility. The Court found no such abuse by Senate President Fernan in recognizing Senator Guingona.
• Hierarchy of Courts — While quo warranto petitions can be filed in RTCs or the Supreme Court, deference to this hierarchy usually impels filing in lower tribunals. The Court noted that for special and important reasons or exceptional circumstances, as in this case involving legislative officers, it has allowed exceptions.
• Internal Rules of Congress — Legislative rules, unlike statutory laws, do not have the imprints of permanence and obligatoriness; they are subject to revocation, modification, or waiver at the pleasure of the body adopting them. Their observance is generally of no concern to the courts. The Court noted the absence of specific Senate rules for selecting a minority leader.

• "The principle of separation of powers ordains that each of the three great branches of government has exclusive cognizance of and is supreme in matters falling within its own constitutionally allocated sphere."
• "Constitutional respect and a becoming regard for the sovereign acts of a coequal branch prevents this Court from prying into the internal workings of the Senate. Where no provision of the Constitution or the laws or even the Rules of the Senate is clearly shown to have been violated, disregarded or overlooked, grave abuse of discretion cannot be imputed to Senate officials for acts done within their competence and authority."
• "This Court will be neither a tyrant nor a wimp; rather, it will remain steadfast and judicious in upholding the rule and majesty of the law."
• "To our mind, the method of choosing who will be such other officers is merely a derivative of the exercise of the prerogative conferred by the aforequoted constitutional provision. Therefore, such method must be prescribed by the Senate itself, not by this Court."
• "On grounds of respect for the basic concept of separation of powers, courts may not intervene in the internal affairs of the legislature; it is not within the province of courts to direct Congress how to do its work."

• Avelino v. Cuenco (83 Phil 17) — Cited by petitioners to support Court's jurisdiction. The Court distinguished it, noting that Avelino involved the interpretation of a constitutional provision on quorum for electing a Senate President and subsequent events justified intervention. In the present case, the Court found no direct constitutional provision governing minority leader selection that was violated.
• Tañada v. Cuenco (103 Phil 1051) — Referenced for its definition of "political question" and the Court's role in determining the validity of selection of Senate Electoral Tribunal members, which was subject to mandatory constitutional limitations, unlike the present case.
• Lansang v. Garcia (42 SCRA 448) — Cited to illustrate the Court's authority to inquire into factual bases for acts of other branches, but with caution not to supplant the other branch's power or wisdom.
• Javellana v. Executive Secretary (50 SCRA 30) — Quoted for its explanation of non-justiciability of political questions based on separation of powers, and that issues of legality or validity of acts, when power is qualified or limited, are justiciable.
• Daza v. Singson (180 SCRA 496), Coseteng v. Mitra Jr. (187 SCRA 377), Guingona Jr. v. Gonzales (214 SCRA 789) — Cited as cases where the Court resolved issues on apportioning seats in the Commission on Appointments, deeming them justiciable as they involved legality prescribed by the Constitution.
• Tañada v. Angara (272 SCRA 18) — Referenced for the principle that where a legislative action is alleged to infringe the Constitution, it is the judiciary's duty to settle the dispute, striking down acts only for unconstitutionality/illegality or grave abuse of discretion.
• Arroyo v. De Venecia (277 SCRA 268) — Cited for the ruling that the Court will not interfere with internal procedures of Congress, assuming good faith and deference to the legislative body's judgment on its own rules, unless a constitutional mandate is violated.
• Acosta v. Flor (5 Phil 18) and Cuyegkeng v. Cruz (108 Phil 1147) — Cited in a footnote (fn 56) regarding the requirement in quo warranto that the petitioner must show entitlement to the office, a point made regarding Petitioner Santiago's standing (rendered moot by Petitioner Tatad's inclusion).

• Article VI, Section 16 (1) of the Constitution — "The Senate shall elect its President and the House of Representatives its Speaker, by a majority vote of all its respective Members. Each House shall choose such other officers as it may deem necessary." Petitioners argued this implies a method for determining the minority and its leader. The Court held it only governs Senate President election and the general power to choose other officers, but not the specific method for the latter.
• Article VIII, Section 1, par. 2 of the Constitution — "Judicial power includes the duty of the courts of justice to settle actual controversies involving rights which are legally demandable and enforceable, and to determine whether or not there has been a grave abuse of discretion amounting to lack or excess of jurisdiction on the part of any branch or instrumentality of the Government." This was the basis for the Court's assertion of jurisdiction to examine the allegations.
• Rule 66, Section 5, Rules of Court — Governs quo warranto petitions by individuals claiming entitlement to a public office. This was the procedural basis for the petition.
• Rules of the Senate (Rules I and II) — Cited to show that while they provide for the election of President, President Pro Tempore, Secretary, and Sergeant-at-Arms by majority vote, they do not provide for the positions of majority and minority leaders or the manner of their selection.
• BP 129, Section 21 (1) — Mentioned in footnote 1 regarding concurrent jurisdiction of RTCs for quo warranto.
• Article VI, Section 16 (3) of the Constitution — "Each House may determine the rules of its proceedings." The Court cited this to emphasize the Senate's power to govern its internal affairs.

• Justice Romero — Reiterated her stance from Tolentino v. Secretary of Finance and Arroyo v. de Venecia that judicial review is permissible only to uphold the Constitution. She found no constitutional breach in this case, as Art. VI, Sec. 16(1) does not support petitioners' interpretation, and the choice of other officers like the Minority Leader is a prerogative of the Senate.
• Justice Vitug — Emphasized that while the 1987 Constitution expanded judicial power to review for grave abuse of discretion, this does not mean the Court should oversee the entire bureaucracy or intrude into every affair of government. He stressed respect for separation of powers and stated that for internal affairs of Congress or the Executive, judicial intervention is warranted only for infringement of a specific Constitutional proscription, which he found lacking here.

• Justice Mendoza (concurring in the judgment but dissenting on jurisdiction) — Argued that the Court has no jurisdiction over the case because the question of who constitutes the minority in the Senate entitled to elect the minority leader is a political question, respecting the internal affairs of a coequal department. He stated that courts have no power to inquire into the internal organization of Congress unless it affects third-party rights or a specific constitutional limitation is involved, neither of which applied here. He distinguished cases where the Court took cognizance as involving specific constitutional provisions (e.g., quorum, composition of electoral tribunals/Commission on Appointments).