I do not know anything about the pub bombing reference. Source?
The landmines were in use from
1985-1987 and were discontinued after civilian deaths were found to be occurring. Also, to accurately define the maliciousness of the landmines used by the African National Congress, you must take the international humanitarian laws at the current time. Landmines were not restricted in internal conflicts by international law. The Convention on Certain Conventional Weapons was set into place on in 1980, but Protocol II was expanded in
May of 1996 to include them in this instance, well after the ANC landmines were used. Also, the
Ottawa Treaty which seeks to eliminate the use of anti-personnel mines around the world, and has been accepted by the international community, did not take place until 1997.
To summarize: The mines were legal by law. They were not used to target civilians, but civilian casualties were suffered. The mines were removed because of civilian casualties. Civilian casualties, even by modern consensus, are a grim, but relatively accepted part of warfare. Nelson Mandela did not himself physically lay mines, but was a part of the leadership of the African National Congress that did.