Whisk together the vinegar, mustard, salt and pepper in a small bowl until combined. Slowly whisk in the olive oil until emulsified and stir in the peppercorns. Let the vinaigrette sit at room temperature for 15 minutes before serving. Vinaigrette can be made up to 8 hours in advance and refrigerated.
Heat the grill to high.
Toss asparagus with the canola oil and season with salt and pepper. Grill until tender, about 5 to 7 minutes.
Place grilled asparagus on a platter and drizzle the vinaigrette over the top.