Idaho didn't want wolves introduced back into the state. The federal government said the state had

no choice. What justification did the federal government give for overriding the state?

that national parks are federal, not state land.

Explanation:

The 1973 Endangered Species Act was designed to protect species of animals and plants which were at risk of extinction. Some people may not like wild species, but it is necessary to maintain the population to prevent the natural environment in the region from collapse. And therefore the federal government reintroduced wolves to the Idaho region by justifying federal rights over the state in this case.