The Federal Debt Collection Practices Act (FDCPA) covers all states, and sets minimum debt collection practices requirements for all debt collectors. Some states have enacted their own versions paralleling the federal FDCPA that apply restrictions more favorable to the consumer, such as Texas. Provided these statutes are not inconsistent with the federal FDCPA, but act only to provide more, rather than less, rights to the consumer, they are law for residents of those states.
Idaho has not, to my knowledge, enacted a separate State law that is substantially different from the FDCPA. They have apparently only enacted legislation to regulate the business practices of collection agencies. They are set forth in Title 26, Chapter 22, sections 2221-2249 of their civil code, and relate mainly to licensing and enforcement provisions.
If your debt collection practices issue does not relate to the licensing and conduct of the business practices of collection agencies, but rather to items such as debt validation procedures, I believe that the controlling law is only the federal FDCPA.