Idaho constitution
Article XVIII
Section 3

No county shall be divided unless
a majority of the qualified electors of the territory proposed to be cut off, voting on
the proposition at a general election, shall vote in favor of such division: provided,
that this section shall not apply to the creation of new counties. No person shall
vote at such election who has not been ninety (90) days a resident of the territory
proposed to be annexed. When any part of a county is stricken off and attached to
another county, the part stricken off shall be held to pay its ratable proportion of all
then existing liabilities of the county from which it is taken.