Preheat oven to 325 F degrees. If using a roasting pan, get it out and lightly spray the rack with cooking spray. If using an oven safe skillet, get it out.
Combine mustard and maple syrup in a small bowl, then put 2/3 of the that mixture in a small bowl, set aside for serving at the table later. The remainder of the sauce will be used for glazing.
Remove pork from brine and pat very dry. Season pork with 1/2 tsp each salt and pepper. Discard brine.
Heat oil in a large, heavy bottomed skillet over MED HIGH heat. Once oil is very hot, add pork and sear about 2-3 minutes per side, until browned.
I like to use a cast iron skillet, so I can take the pan directly from the stovetop to the oven. If you prefer a roasting pan, that will work too.
Lightly glaze pork with some of the maple mustard sauce. Roast pork for 1 hour 15 minutes.
Glaze pork again with maple mustard sauce, then continue to roast another 10 minutes or so. Pork loin is done, and safe, when cooked to an internal temperature of 145 F degrees.
Let pork rest 5-10 minutes, then slice and serve with the bowl of maple mustard sauce you set aside earlier.