Established that slaves were property and that such property was protected by the constitution and thus, could not be restricted in federally controlled territories.

The case referred to in the question is Dred Scott v. Sandford.

Explanation:

Dred Scott was an eslaved man from Virginia who worked for a few years in Huntsville, Alabama. Years later he was taken by his owners to the Missouri territory.

Because the most of the Missouri territory was designated as "free", when his owners tried to take him back slave territory, Dred Scott sued them arguing that having set foot in free territory, he was now a freeman.

The Supreme Court ruled against him: it ruled that black people were not citizens and could not seek the protections and rights that the U.S. constitution granted to citizens.

arresting and exicuting citizens