Worst they'll do is take them if they find them. They'll send you a letter telling you they took the seeds, but that's it. They won't come busting your door down for it. If you're real paranoid use another name or address to send them to, but at the end of the day legal or not, it's just fucking seeds.
On a side note, I probably wouldn't order more than 100-200 dollars of seeds in a single order just in case they do get seized. The drawback is paying for shipping multiple times, but it's better than having one huge order taken.
I use Attitude. Ordered three times now without a hitch. Spent about 100 bucks on each order. I've got enough seeds to last me for about 2 years worth of grows, but if and when I do need seeds again, It'll be Attitude as long as they're still around.
Hope this helps.