Start by heating your grill up. You will want it to reach a temp around 550 degrees F.
Dry the lamb chops with a paper towel. Rub the outside of each rack with dijon first, then sprinkle salt, pepper, and rosemary.
Next, you will want to put the lamb chops on the grill fat side down and close the top. Have a squirt bottle of water handy for this next part. Be CAREFUL. The fat rendering in the hot grill will make the fire flare up. Once you start to see the fire flare up, it is so important to very carefully open the grill and manage the fire with your squirt bottle of water. Then close the lid of the grill again and continue to cook until the fat renders. This will take anywhere from 2-6 minutes depending on how hot the grill is.
Once the fat is rendered and you have a good char on the lamb chops, flip them while you manage the fire carefully. Continue to cook the chops, lid closed, until the third chop in reaches your desired temperature on the chart below:Rare: 115 to 120°F.Medium-rare: 120 to 125°F.Medium: 130 to 135°F.Medium-well: 140 to 145°F.Well-done: 150 to 155°F. Remove and let the lamb chops rest for ten minutes. Slice and serve!