i cant think of any flintlocks that are illegal off the top of my head...so long as they meet the requirements in the regs....
personally, im not a fan of Tradition rifles...my expirience is with a few buddies that have "deer hunters"
the most important part of a flintlock is a the LOCK...without a quality lock, you might as well stay home and save the headaches IMO...the deer hunters i have seen and played with have had TINY frizzens and tiny, odd shaped, shallow pans...what that means is the flint doesnt spark as much because its hitting less metal than a lock with a larger frizzen and flint...
the shallow, odd shaped pan, i dont know i never carried one hunting...but i like the deep pan on my TC..the lock is key to a good shooting flinter...its gotta throw a good spark and gotta throw that spark every time its fired and its gotta land in the pan...the spark gotta be hot enough to ignite the priming powder...and the lock has to be fast...cheap locks often lack in all those departments which leads to misfires, hang fires, slow locks and misses...
alot of guys that arent expirienced with a flinter have troubles getting them to fire and being accurate with them...the reason almost always comes back to the lock..even a good lock not used or cared for properly will give headaches..but a quality lock will do its job if the shooter does theres...cant polish a turd...cant make a crappy lock fire like a good lock..
i also do not care a whole lot for single triggers on flintlocks...after shooting a rifle with double triggers it'll be hard if not impossible to get me to own a flinter without them...it makes them that much easier to shoot...a personal thing i guess...but i like a hair trigger on a flinter...
for a starter rifle id recommend looking into a lyman or a TC...ive never shot a lyman but hear great things about them...i own a TC Hawken...i picked it up used for a pretty dang good price...like 1/3 or so of the new price...probably because its a pretty early model...but i inspected it, and someone took VERY good care of it...
if your shopping for a used flinter, theres some things to look at...the beauty of shopping used is a quick glance and you can almost tell if it was taken care of properly or not...hard to hide effects of black powder that wasnt properly cleaned..flinters are pretty simple...lock, stock, and barrel...as long as the stock is structurally sound(no cracks etc) and you can live with its looks, its on to the barrel...only barrels ive heard of issues on are CVAs and i dont know enough about the issues to talk about them...just know where were some issues with their muzzleloaders in the past...so if its cleaned inside and out and not rusted and pitted, the barrel aughta be fine....so that leaves the lock...and trigger(s)..a used rifle may need the frizzen replaced but thats 2 screws and a 20$ part...
TCs have a lifetime warranty...as long as its a TC product, they will make it right as long as its not something like "my rifle got ran over by a truck and was fired and wasnt cleaned for 8 years while stored in a damp basement now it wont fire.." not sure of the other production flinters warranties etc...
lots of good guys here that can give good advice...im no expert and dont proclaim to be...just passing on my opinions...good luck!! remember, black powder smoke is addictive!! once you start flintin, you'll be in love so long as you take the time to learn to shoot a flinter...if you dont, it'll be frustrating and not worth getting into...alot of guys dont take the time to learn and that leads to misfires and poor shooting...