Why did popular sovereignty unconstitutional according to the dred Scott decision?

In the Dred Scott decision of 1857, the Supreme Court ruled that popular sovereignty—allowing territories to decide for themselves whether to permit slavery—was unconstitutional because it violated the Fifth Amendment. The Court argued that Congress did not have the authority to prohibit slavery in the territories, as doing so would deprive slaveholders of their property rights without due process. This ruling effectively nullified the principle of popular sovereignty and intensified the national debate over slavery.