A REQUIREMENT for review written into anti-apartheid legislation enacted last year is putting the question of sanctions against South Africa back on the political agenda. It's a debate for which there is no serious need. There is scant agreement on whether the sanctions voted last year (over a presidential veto) were wise. The Reagan administration feels they haven't worked and won't, and some part of the Congress feels they haven't worked and will -- if they are strengthened. Many others who detest apartheid are agnostic. A year's experience has shown sanctions cut both ways: they push the ruling white minority toward reform, but they also stiffen its resistance. Before considering new sanctions, more time and evidence are needed to calculate the net effect of old ones.

There is genuine uncertainty about which external actions promote and which retard internal change. Still, what is clear is that South Africa is not only a society being daily torn apart by apartheid but also one being increasingly touched by impulses toward reform. Whether these will produce a sustained wave is the great question. It is evident that the various sources of change inside and outside South Africa are making a mark. Look at the items listed by Secretary of State George Shultz in a speech on Sept. 29: the new Indaba constitutional proposals negotiated by all racial groups in Natal, the meetings of Afrikaners and the African National Congress, negotiations across racial lines by black trade unions and other groups. Any strategic view must take into account the reality of apartheid's horrors and the potential of developments like these.

In his speech Mr. Shultz reaffirmed the administration view that the primary sources of change in South Africa are internal and that American influence is necessarily limited. He took the occasion to present a democratic vision of South Africa's future and to summarize the contribution the United States intends to keep making by its openness to all peaceful groups, by its aid to black projects and by its forward-looking private business presence.

Some critics view the administration approach as a cop-out, or worse. We disagree. The administration's effort to keep the policy, and the policy debate, within consensual bounds makes sense.