"Permits
Only two places on the trail require a permit: Shenandoah and Great Smoky Mountains National Parks. SNP is free and obtained at the front entrance. The Smokies have a new permit system as of Feb 2013.."
The link goes to a page that has
"Think that covers it..no?
Appalachian Trail Thru-Hiker Backcountry Permit on the top.