COL. QADDAFI, the Libyan dictator, has spent the better part of the last few years alienating the few remaining African and Arab states that would still give him the time of day. But notwithstanding the scorn and isolation he has brought on his country, his oil money, Soviet connection and imperial pretensions give him a continuing potential for troublemaking. In his latest adventure, he has sponsored, not for the first time, an invasion of Chad, the largely barren African state lying to Libya's south. He has trained, armed and, evidently, provided artillery cover to a rebel group led by former president Goukouni Oueddei, who has carried the battle against his longtime rival, president Hissene Habre, deep inside Chad.

The assault is the crueler for coming at a time when, after years of upheaval, the country was returning to what Post reporter Leon Dash called last December a tenuous tranquility. The former French colony sits astride the difficult political divide between northern Moslems and southern Christian blacks, and it was starting to give priority to its desperate need for reconciliation. Donors of development aid were getting in line.

Col. Qaddafi, however, was able to play on political and tribal rivalries and to put the president whom Mr. Habre had deposed, Mr. Goukouni, back into battle. It may be true that, in the absence of elections, it is not easy to say why one rather than the other deserves to be president. But certainly the Libyan marauder has no right to make the choice.

A difficult place to rule, Chad is, for many of the same reasons, a difficult place to conquer. Vast, landlocked and in the main little developed, the country has always needed an outside support system. Fortunately, its other neighbors see a menace in the Libyan intervention and, in their various ways, they are doing something about it. France, the former colonial power, has been stirred to provide extra aid, including "civilian technicians." The United States seems, nervously, just to be encouraging others to keep Col. Qaddafi from changing the political face of Africa.