Some regions will be like restricted airspace except without the air, so to speak. Pulling missions for factions will endear you to them and they won't pop you just for being there. Ofc that can make other areas tougher to get to, as you can't be everyone's BFF on the IFF. Permits grant you access to an even more restricted place within that space, like a prison or such. And some of the galaxy is roped off for future development, like the inevitable Thargoids.
Early-in backers get a free permit to travel to Sol. IDK the game mechanics around how to obtain the Sol permit ingame; or if sneaking would even work for Sol though it'd be cool if it did. I'll try to cover your back on your FSD jump out-system if it's too hot to visit "unannounced".
I was hoping they wouldn't make it like a invisible wall unless you had the magic card but to make it more a gameplay feature where you "can" but you might need help without a permission slip.