Legislative or administrative decision? And why?

An Idaho case from Patty Salkin's (Albany) Law of the Land blog, "County’s Decision on Whether to Amend Comprehensive Plan Not Reviewable by Court":

The Supreme Court of Idaho held that because there is no statute authorizing judicial review of the legislative decision whether or not to amend a comprehensive plan, the courts may not review the Board’s actions. The Court noted that a county board of commissioners is not an “agency” under the Idaho Administrative Procedures Act (IAPA), and that therefore its actions are not reviewable absent a statute invoking judicial review provisions of the IAPA. The Court said that a request to amend zoning is not an “application for a permit” which would have provided for judicial review, noting that “An application for a zoning change, like a request for an amendment to a comprehensive plan, is not an application for a ‘permit’ and thus no review is authorized…” Lastly, the Court commented that although this legislative decision is not subject to judicial review, it could be subject to scrutiny by means of collateral actions such as declaratory actions.

The definitions of "legislative decisions" and "administrative decisions vary from jurisdiction to jurisdiction. YMMV. EMM