Simple Green sprayed full strength directly on the clothing, really hose it down with it, let it soak for a while to break the fuel down, then wash it in your normal washing machine. Should be fine. May not want to wash anything else with it in the same load though, depending on how bad it is.
Decades ago when I was in the service, Mrs. Slim used to wash my fatigues separate, and it would take 2 trips through the washing machine to get all the diesel out. This was with the old granular Tide laundry soap. Then she'd have to run a "load" of nothing but laundry soap and water to rinse it all out of the washing machine before she put any "good" clothes in it.