Preheat a grill or grill pan to medium-high heat.
Season the chicken breast evenly with the garlic powder and half of the sea salt and black pepper.
Grill the chicken for 6 to 7 minutes per side until the internal temperature reaches 165°F, then set aside to rest.
Lightly brush the romaine hearts and asparagus spears with one teaspoon of the olive oil.
Place the asparagus on the grill for 4 to 5 minutes and the romaine hearts for 1 to 2 minutes until they are lightly charred and tender.
In a small bowl, whisk together the remaining olive oil, lemon juice, lemon zest, Dijon mustard, and the remaining salt and pepper.
Slice the grilled chicken into strips and chop the charred romaine and asparagus into bite-sized pieces.
Combine the grilled vegetables, chickpeas, and chicken in a large bowl, drizzle with the lemon vinaigrette, and toss gently to coat.