They're not illegal in the US, just the US FDA frowns upon them for some reason. I have not heard of customs withholding circle lenses. They shouldn't as it's not considered hazardous to the US (like illegal drugs and explosives), and they can't prove if you have or have not given your prescription to the company to have it confirmed. As long as you properly care for your lenses you shouldn't have to worry about any troubles with your eyes.
Pinky Paradise is a site I see constantly referred to for ordering circle lenses. I haven't heard of any horrible experiences from them, so I'm sure they're safe to order from, and sell KFDA approved lenses. You should be able to use OptiFree just fine with the circle lenses, as they're made from the same materials as regular clear lenses.
Every time I open the fridge, the hole in my jello glares at me.
Thank you for completely removing my signature without emailing me that it was too long.