New Delhi, Aug. 7 -- The Union government on Thursday opposed a plea in the Supreme Court seeking an income-based sub-quota within reserved categories, contending that the constitutional architecture of reservations for Scheduled Castes (SCs), Scheduled Tribes (STs) and Other Backward Classes (OBCs) is founded on historical and social disadvantage and cannot be restructured solely on the basis of economic criteria. The Centre also opposed extending the "creamy layer" principle to SCs and STs, arguing that Supreme Court precedent has consistently confined the doctrine to Other Backward Classes (OBCs). In a counter affidavit filed through the department of social justice and empowerment, the Centre argued that the petitions seek judicial dire...