Related Rule
Practice Relating to Rule 99. Deprivation of Liberty
Section A. General
The Philippine National Police (PNP) Manual on Ethical Doctrine (1995) provides:
Respect for Human Rights – In the performance of duty, PNP members shall respect and protect human dignity and uphold the human rights of all persons. No member shall inflict, instigate or tolerate extrajudicial killings, arbitrary arrests, any act of torture or other cruel, inhuman or degrading treatment or punishment, and shall not invoke superior orders or exceptional circumstances such as a state-of-war, a threat to national security, internal political instability or any public emergency as a justification for committing such human rights violations. 
Philippines, Manual on Ethical Doctrine, PNPM-0-0-8-95 (DHRDD), Directorate for Human Resource and Doctrine Development, National Headquarters, Philippine National Police, Revised, August 1995 Edition, Section 2.9.
The Philippine Army Soldier’s Handbook on Human Rights and International Humanitarian Law (2006) provides:
While not in combat:
3. As a general rule, arrest/search may be effected following the constitutional precepts found in Section 2 Article III of the Constitution to wit: Section 2 The right of the people to be secure in their persons, houses, papers and effects against unreasonable searches and seizures shall be inviolable, and no search warrant or warrant of arrest shall issue except upon probable cause to be personally determined by the judge after the examinations under oath of affirmation of the complainant and the witnesses he produces and particularly describing the place to be searched and persons or things to be seized.” There are situations, however when you can apprehend without warrant of arrest:
a. When, in his presence, the person to be arrested has committed, is actually committing, or is attempting to commit an offense;
b. When an offense has in fact been committed and he has reasonable ground to believe that the person to be arrested has committed it; and
c. When the person to be arrested is a prisoner who has escaped [from] a penal establishment or place where he is serving final judgment or temporarily confined while his case is pending, or has escaped while being transferred from one confinement to another.
But generally, you cannot apprehend or detain a person arbitrar[ily], or just with a mere suspicion that he is insurgent. 
Philippines, Philippine Army Soldiers Handbook on Human Rights and International Humanitarian Law, A Practical Guide for Internal Security Operations, 2006, pp. 54–55, § 3.
In its glossary, the Handbook further notes: “Arbitrary detention – The seizure [or] holding of a person in custody by means that do not conform to established human rights standards or that is perpetrated in pursuance of orders, legislation or practices that violate those standards.” 
Philippines, Philippine Army Soldiers Handbook on Human Rights and International Humanitarian Law, A Practical Guide for Internal Security Operations, 2006, p. 67, Glossary.
The Philippines’ Republic Act No. 8438 (1997) provides: “The regional government [of the Cordillera Autonomous Region] shall take measures to prevent torture; other cruel, inhuman, and degrading treatment or punishment; and illegal detention and extra-judicial executions.” 
Philippines, Republic Act No. 8438, 1997, Section 27.
In its judgment in the Cayao case in 1993, the Philippine Supreme Court stated:
While it is true that complainant was not put behind bars as respondent had intended, however, complainant was not allowed to leave the premises of the jail house. The idea of confinement is not synonymous only with incarceration inside a jail cell. It is enough to qualify as confinement that a man be restrained, either morally or physically, of his personal liberty … Under the circumstances, respondent judge was in fact guilty of arbitrary detention when he, as a public officer, ordered the arrest and detention of complainant without legal grounds. 
Philippines, Supreme Court, Cayao case, Judgment, 15 September 1993.
In the Flores case before the Philippine Supreme Court in 2001, in which the appellants (three members of a Citizen Armed Force Geographical Unit (CAFGU)) appealed the decision of a lower court that had convicted them of the crime of kidnapping and serious illegal detention, the court reversed and set aside the lower court’s decision and ordered their immediate release from confinement. In doing so, the court noted:
Arbitrary detention is committed by any public officer or employee who, without legal grounds, detains a person …
As far back as the case of U.S. v. Cabanag, it was held that in the crime of illegal or arbitrary detention, it is essential that there is actual confinement or restriction of the person of the offended party. The deprivation of liberty must be proved, just as the intent of the accused to deprive the victim of his liberty must also be established by indubitable proof. In the more recent case of People v. Fajardo, this Court reiterated the ruling in U.S. v. Cabanag, i.e., there must be uncontroverted proof of both intent to deprive the victim of his liberty, as well as actual confinement or restriction.
Detention is defined as the actual confinement of a person in an enclosure, or in any manner detaining and depriving him of his liberty. 
Philippines, Supreme Court, Flores case, Judgment, 31 May 2001.
In the Astorga case before the Philippine Supreme Court in 2003, in which the petitioner sought the reversal of a lower court’s decision which had found him guilty of arbitrary detention (as Municipal Mayor of Daram, a public office, he had unlawfully detained a five-member government team investigating illegal logging operations), the court denied the petition. In its judgment, the Supreme Court noted:
Arbitrary Detention is committed by any public officer or employee who, without legal grounds, detains a person. The elements of the crime are:
1. That the offender is a public officer or employee.
2. That he detains a person.
3. That the detention is without legal grounds.
That petitioner, at the time he committed the acts assailed herein, was then Mayor of Daram, Samar is not disputed. Hence, the first element of Arbitrary Detention, that the offender is a public officer or employee, is undeniably present.
Also, the records are bereft of any allegation on the part of petitioner that his acts were spurred by some legal purpose. On the contrary, he admitted that his acts were motivated by his “instinct for self-preservation” and the feeling that he was being “singled out.” The detention was thus without legal grounds, thereby satisfying the third element enumerated above.
What remains is the determination of whether or not the team was actually detained.
The prevailing jurisprudence on kidnapping and illegal detention is that the curtailment of the victim’s liberty need not involve any physical restraint upon the victim’s person. If the acts and actuations of the accused can produce such fear in the mind of the victim sufficient to paralyze the latter, to the extent that the victim is compelled to limit his own actions and movements in accordance with the wishes of the accused, then the victim is, for all intents and purposes, detained against his will.
In the case at bar, the restraint resulting from fear is evident. In spite of their pleas, the witnesses and the complainants were not allowed by petitioner to go home. This refusal was quickly followed by the call for and arrival of almost a dozen “reinforcements,” all armed with military-issue rifles, who proceeded to encircle the team, weapons pointed at the complainants and the witnesses. Given such circumstances, we give credence to SPO1 [Senior Police Officer I] Capoquian’s statement that it was not “safe” to refuse Mayor Astorga’s orders. It was not just the presence of the armed men, but also the evident effect these gunmen had on the actions of the team which proves that fear was indeed instilled in the minds of the team members, to the extent that they felt compelled to stay in Brgy. Lucob-Lucob. The intent to prevent the departure of the complainants and witnesses against their will is thus clear. 
Philippines, Supreme Court, Astorga case, Judgment, 1 October 2003.
[emphasis in original]
In 1988, the Human Rights Commission of the Philippines declared that all people residing in the Philippines had the right not to be detained unlawfully, and when detained, they could not be held in secret detention places, in solitary confinement or incommunicado or be subjected to other similar forms of detention. 
UN Secretary-General, Report on information submitted by Governments pursuant to Sub-Commission Res. 7 (XXVII) of 20 August 1974, UN Doc. E/CN.4/Sub.2/1990/20, 19 July 1990, §§ 2, 11 and 15.