Al-Shabaab terrorist group’s series of kidnappings and cross-border incursions into Kenya threatened security and the lucrative tourism industry in East Africa's largest economy. Towards the end of 2011 events like the kidnapping of two foreigners and the killing of another in the Kenyan resorts on the east coast, the abduction of two aid workers from the Dadaab refugee camp, and the attack against Kenyan soldiers in cross-border raids raised a lot of concern for the Kenyan government. Consequently, the latter decided that the national security interest of Kenya had to be protected. As a result, the decision of the government was to go to war against Al- Shabaab. This prompted the Kenya Defence Forces’ (KDF) incursion to Somalia in a pre-emptive and preventive campaign aimed at fl ushing out Al-Shabaab from this country. The campaign took off in mid-October 2011 and it was dubbed “Operation Linda Nchi”, Swahili for “Protect the country’. In this article we look at the implication of Kenya’s pre-emptive and preventive incursion against Al- Shabaab from the perspective of international law.