Which phrase best defines eminent domain?

Eminent domain is best defined as the power of the state or federal government to take private land without the owner's consent, which aligns with the correct choice. This authority allows the government to acquire private property for public use, provided that they compensate the owner fairly according to the Fifth Amendment of the U.S. Constitution. The principle behind eminent domain is that the government can take land for initiatives like building highways, schools, or parks, which ultimately serve the public interest.

The other options refer to different governmental powers that do not relate to land acquisition. The first option addresses the government's taxing authority, while the second focuses on creating tariffs. The last option involves the regulation of interstate commerce, which pertains to trade between states rather than the acquisition of land. Thus, while these functions are important aspects of governmental power, they do not encompass the specific concept of eminent domain.