WHY DOES Turkey's military government keep locking up its three-time elected prime minister, Bulent Ecevit? He is no terrorist of the sort whose depredations forced the generals to seize power in 1980. He is a certified democrat, humanist and lover of liberty, the single Turk who most represents to Westerners the values Turks share with the West. It is conceivable that Mr. Ecevit, aware that his fate is followed from afar, is deliberating testing the regime's democratic protestations. But the proper way for the regime to react is not to lock him up. It is to let him out in order to prove its own promise of an early return to representative rule.

Turks look West uncertain whether to ask for deference on account of their Byzantine and Islamic roots or to demand equal treatment for having had strong links to Europe for at least two centuries. They want it realized that they have special problems arising from their special geographical and economic place, but they insist on not being taken as second-class citizens of the Western alliance. It is a difficult act to carry off, and the Western democracies have good reason to respect the effort the Turks have made. This regime has suppressed a terrorist movement of a ferocity unimaginable in the West, turned around a desperate economy and moved toward its goal of elections by early 1984.

The more's the pity, then, that Turks show such surprise when their friends occasionally evince unhappiness over what looks like unaccountable backsliding. The West's understanding of the imperatives of the Turkish crisis--an understanding expressed in substantial material as well as political terms--surely has won it a right to speak up when it feels Turkey has gone too far. Questions about the fate of Mr. Ecevit and other prominent democratic prisoners, or about some of the means used to root out subversion, are entirely legitimate. Yet too often Turks react to them as though their very honor had been fatally impaired. They should, rather, understand that their allies are no less eager than they themselves profess to be to see them return to the democratic fold. They should let Mr. Ecevit go free--now.