A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Can I have more than one Fortification attached to a province, such as "The Tower of Vigilance"?
The Tower of Vigilance Holding Gold Cost: 0
Fortification (Fortifications attach, straightened, to the Province from which they entered play.) Engage, [BOW]: If you have any units at this battlefield, create a 0F/2C/2PH Samurai • Guard Personality there. Remove him from the game after this battle ends.
Can I have more than one Fortification attached to a province, such as "The Tower of Vigilance"?
The Tower of Vigilance Holding Gold Cost: 0
Fortification (Fortifications attach, straightened, to the Province from which they entered play.) Engage, [BOW]: If you have any units at this battlefield, create a 0F/2C/2PH Samurai • Guard Personality there. Remove him from the game after this battle ends.
Under Discussion.
As per today's Rules Sheet errata, there are no restrictions or limitations on attaching Fortifications to a province, as long as you can meet their normal entering play requirements.
Please note: this is different than the previous Legacy Rule regarding Fortifications, which limited them to one per card name per province.