It is permissible for a Muslim country to cooperate with non-Muslim countries to combat terrorism
Al-ʿAllāmah Aḥmad Ibn Yaḥya al-Najmī
cooperating with non-Muslims to stop the terrorists sh najmi
Al-ʿAllāmah Aḥmad Ibn Yaḥya al-Najmī (may Allāh have mercy upon him) stated,
“I have already written an edict pertaining to this matter, which contains a comprehensive discussion on this issue. This is because some people deem cooperating with non-Muslim nations to combat terrorism, which Allāh and His Messenger has forbidden, to be an act of disbelief and apostasy.
The truth, which must be acknowledged, is that if a group from the non-Muslims appeal to us to cooperate with them and for them to cooperate with us to combat something that Islam forbids and commands for it to be fought and stopped, then it is permissible for us to do this.
If they present to us an offer to stop usury for example or to combat terrorism –which are the bombings perpetrated by some individuals from the Muslims and which they claim to be an act of worship – then we say that we will cooperate with them [to achieve this].”
Abū ʿAbdullāh Ḥasan al-Ṣomālī
Masjid Al-Sunnah Al-Nabawīyah
Philadelphia, PA, USA
23/10/2014 [29th Dhū al-Ḥijjah 1435]
 Fatḥ al-Rabb al-Ghafūr Dhī al-Raḥmāh, p. 81-81.