BEFORE HE FLED last year, the wretched Idi Amin virtually disemboweled Uganda, destroying its inner political and economic structure and ravaging the people and the land. Reconstruction has been a prodigious task. The first requirement, on which all others must necessarily be based, has been to constitute a working legitimate source of political authority. Unfortunately, this has yet to be done.

Tanzania's army, which liberated Uganda, set up an interim national council that appointed a civilian president. Inevitably, a tug of war developed between these two sources of authority. In the latest clash, President Godfrey Binaisa, on a risky second try, dismissed army chief of staff David Oytie Ojok, a general linked with pre-Amin president Milton Obote. Mr. Binaisa said that the general had not settled down the country's security situation. Mr. Binaisa, who intends to run for president, may also have had it in mind to get rid of the general (by appointing him to a distant ambassadorship) before Mr. Obote returns from Tanzanian exile to start campaigning against him in the elections scheduled for next December.

The general's colleagues in the national council's military commission, however, then dismissed Mr. Binaisa, who evidently still intends to campaign against Mr. Obote for the elective presidency.

In fact, there are two sets of soldiers in Uganda, and each will have something to do with the key question of whether the election is fair and whether Ugandans and their neighbors regard it as fair. There are the Ugandan armed forces, reconstituted and trained by the Tanzanian army, and there is the Tanzanian army. Ideally, they Ugandan soldiers would simply hold the ring while the politicians compete. If this happens, it will be a pleasant surprise. Ideally, too, the Tanzanian army, having defeated Amin and helped Uganda start to get back on its feet, would complete its pullout before the elections. This would spare Tanzania the charge of having kept troops in Uganda to facilitate the election of Julius Nyerere's friend Milton Obote.

Elsewhere in Africa, international observers have been found helpful in assuring that elections are fair and that their results are respected. Uganda would seem to be just the right place for this procedure. It desperately needs the sort of broadly based legitimate government that alone will give it a fair chance to tackle its monumental reconstruction concerns.