How did the Security Council use a mandatory arms embargo against South Africa in 1977?

In 1977, the United Nations Security Council imposed a mandatory arms embargo against South Africa in response to the government's apartheid policies and the suppression of internal dissent.1

This international measure was intended to isolate the regime and restrict its military capabilities. However, the South African government sought to mitigate the impact of the embargo by developing its own domestic weapons industry. Through the state-owned Armaments Corporation of South Africa (Armscor) and a network of private and government-controlled corporations, the country successfully developed a variety of new weapons systems to overcome the effects of the international restrictions.1

While the embargo aimed to pressure the state to abandon its discriminatory policies, the government simultaneously pursued the development of nuclear weapons in extreme secrecy during the 1970s and 1980s, though these were eventually dismantled by 1990.21