Final answer:
De jure segregation refers to the legally enforced separation of groups, as seen in US Jim Crow laws and South African apartheid, upheld by 'separate but equal' doctrine until overturned by Brown v. Board of Education.
Step-by-step explanation:
Segregation that occurs because of laws or administrative decisions is known as de jure segregation. This type of segregation was legally sanctioned and enforced, exemplified by the Jim Crow laws in the United States and apartheid in South Africa. In the landmark Supreme Court case Plessy v. Ferguson, 'separate but equal' facilities were deemed constitutional, upholding de jure segregation across public and private spheres.
It was not until the Brown v. Board of Education case in 1954 that the Supreme Court declared that 'separate educational facilities are inherently unequal,' indicating the start of the end of legalized racial segregation in the U.S. However, challenging and dismantling de facto segregation, segregation by practice without legal backing, remains a complex issue reflecting ingrained societal prejudices and inequality.