She can choose to display "fairness" by defending to the hilt the right of the prime suspects to all the legal defenses they are allowed. Arroyo can suggest police and prosecutors show due respect for all those implicated in the massacre by not questioning them too severely.
Or she and the commanders of the armed forces and national police can act decisively and invade the compounds of powerful clan members, question all of them and their aides, arrest suspects, seize records, and drive those involved out of government and politics.
Even as Arroyo ordered a state of emergency surrounding the area of the massacre site, questions have arisen about her will to act, consistent with "a culture of impunity" against law and order that has become entrenched over many years of misrule.
Killings may be more frequent in the Muslim south, but they also go on everywhere else where hereditary families control wide swaths of land and hold the levers of power in the hierarchy of government and business.
"The government definitely has the numbers, but not the political will," said Vilnor Papa, Philippine campaign manager of Amnesty International. "We have political killings. We have summary executions."
This time, the massacre was excessive even by local standards, culminating in the highest death toll in modern Philippine history. It happened brazenly in a daylight attack, seen by witnesses, in which the kidnappers and killers evidently faced no threat from local police, who according to some accounts may have been involved in the massacre.
After initial flurries of headlines, prayers and denunciations, killings of one or two people in the country's violent southern regions are usually soon forgotten. But this one undoubtedly will endure in memory as emblematic of much deeper problems.
The killers apparently were not from the armed forces, but were alleged agents of the mayor of the town of Ampatuan that bears his family's name. The Ampatuan mayor, Andal Ampatuan Jr, eager to succeed his father as governor of Maguindanao province, faced a potential electoral challenge from a rival clan leader, Ismael Mangudadatu, vice mayor of a nearby town who refused to stand down amid threats to his life.
Assuming gunmen would be reluctant to shoot women and journalists, Mangudadatu sent his wife and two sisters, accompanied by a number of other women as well as local reporters, to register his candidacy with the local election commission. The victims were riding in a convoy through Ampatuan when 100 or so gunmen herded them off, killing the wife and sisters, a number of other women and about 30 journalists.
Mayor Ampatuan, his accusers claim, acted as though he had little fear of legal retribution. In a region barely subdued by Spanish and then American colonialists, warlordism has replaced old-style feudalism, with extended family groupings fighting tenaciously for political perks, privileges and payoffs.
After the killings, Arroyo's government was quick to distance itself from the Ampatuan family, denouncing the deed as "unconscionable" and declaring no one "untouchable". But the link between rulers and killers seemed clear Ñ the provincial police chief and three other officers were seen earlier with the gunmen, according to local news reports.
Now in jail in Manila facing trial for multiple murders, Mayor Ampatuan does not seem to have been questioned very rigorously. Free to give interviews through the bars of a cell that he shares with 16 other suspected criminals, he has blamed the mass murder on a familiar target, the Moro Islamic Liberation Front (MILF) rebel group.
He is said to have 40 lawyers on side, churning out the legal paperwork to ensure that he won't go on trial any time soon Ñ if ever. His older brother, Zaldy, ensconced as governor of the Autonomous Region of Muslim Mindanao (ARMM), also seems anxious to help.
The ARMM, set up years ago to satisfy demands of Muslim leaders in Mindanao, serves as a conduit for wheeling and dealing between Manila and the ARMM's half-dozen member provinces and lesser fiefdoms. On a compound in the city of Cotabato, next to Maguindanao, the ARMM headquarters provides a perch from which ARMM Governor Zaldy Ampatuan has issued statements calling for "fair play" and rallying loyalists to his brother's defense.
The web of compromises that catapulted Arroyo to an election win in 2004 means she is unlikely to go beyond headline-grabbing words and a highly publicized manhunt, all routine whenever a political killing occurs in the Philippines, while leaving the Ampatuans in power.
The Ampatuan political machine, led by the governor, had guaranteed vast majorities in the province for Arroyo and her followers. In the 2004 presidential election, she won 100% of the votes in some towns Ñ at some polling stations the number of votes for her exceeded that of registered voters Ñ and her candidates in Maguindanao won easy majorities in the 2007 mid-term elections for the Philippine Congress.
Hope for justice, however slim, may lie in the uproar over the massacre Ñ and the fact that Arroyo cannot under the Philippine constitution run for another term as president and may not feel obligated to the Ampatuan family to deliver the votes for her anointed successor candidate.
Since so many local journalists were killed, Arroyo faces pressure not only from the Philippines' National Union of Journalists, but also from international organizations such as Reporters Without Borders (Reporters sans frontiers) and the Committee to Protect Journalists, both of which have strongly condemned what happened.
"There is pressure from all sectors for the government to do something," said Girlie Padilla, secretary general of the Ecumenical Movement for Justice and Peace. But she is not optimistic. "Will they cover up for the ally who did the killings?" she asked rhetorically. "They would do anything to cover up for this group. We will have a hard time getting justice."
The whole crisis in law and order is deepened by the poverty of the area, an agricultural region where most people subsist below the poverty line and at the mercy of corrupt landlords and officials. They enforce control through their own private armies, many of whose foot soldiers also serve in the armed forces or police.
In this environment, extremist propaganda inevitably draws some into the insurgent MILF. The fact that the government now has 3,000 troops in the area, many of them in pursuit of Muslim guerrillas who apparently had nothing to do with the massacre, adds to the sense of frustration among those hoping for justice.
Arroyo feels she has to keep Muslim family leaders on side while soldiers battle the MILF, which is still deeply rooted in camps in remote regions. The Ampatuan family, in turn, has ties to another large Muslim grouping, the Moro National Liberation Front, which over the years has made, and broken, its own ceasefire arrangements with the government.
"The area is highly militarized," said Satur Ocampo, a long-time foe of the government who now serves as deputy leader of the opposition in the Philippines House of Representatives. "The Philippine National Police was on alert, but it's quite apparent they were unable to prevent this massacre." While the police "talk about collecting firearms", he said, "heavily armed bodyguards and politicians can perpetrate this action without law enforcement".
Donald Kirk, a long-time journalist in Asia, is author of Philippines in Crisis: US Power versus Local Revolt and Looted: the Philippines After the Bases.
