Combine mayonnaise, Dijon mustard, garlic, lemon zest, lemon juice, and garlic salt in a bowl and mix well. Refrigerate lemon aioli until ready to use.
Preheat an outdoor grill for medium heat and lightly oil the grate.
Divide asparagus stalks into groups of 3 to 5 stalks, depending on the thickness of the asparagus. Wrap each asparagus bundle tightly with 1 piece of bacon, overlapping slightly as you wrap and tucking the ends under the bacon so it holds securely.
Place asparagus bundles in a single layer on a piece of aluminum foil. Spray bundles lightly with olive oil spray and top the bacon with cracked pepper.
Grill asparagus bundles on the foil for 10 minutes. Flip each bundle and grill until bacon is cooked through and crisp, an additional 10 minutes. Serve with lemon aioli.
