Heat the grill to high. Remove the corn from the water and shake off the excess water.
Put the corn on the grill, close the cover, and grill, turning every 5 minutes, until the kernels are tender when pieced with a paring knife, about 15 to 20 minutes.
While the corn is cooking, whisk together the vinegar, mustard, honey, chives and salt and pepper, to taste, in a medium bowl until combined. Slowly whisk in the oil until emulsified. Stir in the scallions and set aside.
Stand the corn upright on its stalk end and carefully cut down the sides of the cob with a sharp chef's knife, trying to keep the corn in sheets. Carefully transfer the corn to a platter and drizzle with the vinaigrette.