Constitution of Kenya
188. Boundaries of counties
(1) The boundaries of a county may be altered only by a resolution--
(a) recommended by an independent commission set up for that purpose by Parliament; and
(b) passed by--
(i) the National Assembly, with the support of at least two-thirds of all of the members of the Assembly; and
(ii) the Senate, with the support of at least two-thirds of all of the county delegations.
(2) The boundaries of a county may be altered to take into account--
(a) population density and demographic trends;
(b) physical and human infrastructure;
(c) historical and cultural ties;
(d) the cost of administration;
(e) the views of the communities affected;
(f) the objects of devolution of government; and
(g) geographical features.