Now, I get that strict is core, forward. My question is on the legality of cards fixed to starters?
Strict.
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.
Now, I get that strict is core, forward. My question is on the legality of cards fixed to starters?
Starter deck reprints are not allowed in the Strict format.
One way to think of Strict-legal cards (for 2014 anyway), are any cards that have the Dark Blue Ivory Edition legality bugs printed on them. Granted there are exceptions to this rule (Ivory Edition Strongholds/Sensei, promos which are not considered legal yet, etc.), but it's an easy rule of thumb for most cards.