These youths are dangerous for a number of reasons. One, they are trained militants, and secondly, they are now out of work.
Two things will most certainly happen, both prompted by the two aspects of the returning jihadists socioeconomic situation.
They will engage in criminal activities to earn a living or most certainly continue their association with local jihadists (affiliates of Al-Shabaab terror group, particularly Al-Muhajiroun).
The new terror affiliate is versatile and very well embedded in the top leadership of the Al-Shabaab. This ensures it gets briefs about the ideal strategies besides funding for operations.
Conecting with local terror networks will make the returning terrorists more at home besides equally lethal.
What is most important is that, the returning terrorists are at home. They know the terrain and every target Al-Shabaab has mapped. This is the truly profound. Kenya will face a serious challenge of homegrown terrorism.
Tracking down returning jihadists and conducting 24hrs surveillance on them is an expensive venture, however, it is the only solution Kenya may have to solve the threat of homegrown terrorism.