1. In a large glass or stainless-steel bowl, whisk together the lemon juice, mustard, salt, and pepper. Add the oil slowly, whisking.
2. In a medium glass or stainless-steel bowl, combine the tuna and chickpeas. Gently stir in 1/4 cup of the dressing.
3. Using a stainless-steel knife, peel the oranges down to the flesh, removing all of the white pith. Cut the sections away from the membranes and set aside. Squeeze 2 tablespoons of the juice from the membranes into the remaining dressing.
4. Add the tuna and chickpeas, orange sections, lettuce, fennel, onion, jalapeño, and cilantro to the dressing and toss gently.
Wine Recommendation: Instead of the more traditional riesling, accompany this tuna with a Pfalz spätlese made from scheurebe. The wine's wild, even exotic scents of grapefruit, orange peel, minerals, and flint will be a pleasant and harmonious surprise.