Do you have a habit of posting opinions about things you're unfamiliar with? Or just repeating someone else's poorly informed opinion, like in the other thread?
Digital/electronic triggers are not illegal.
Tony, I stumbled across the setup the OP is talking about the other day, but forget the name now. It's a newer company. Apparently they have ATF approval for a pull & release trigger system, that can be set for either normal semi or pull+release. They used a standard "mil-spec" semi-auto FCG modified with an electronic method of actuating the sear; supposedly it works as a normal trigger if the batteries die. It looked interesting enough, but not cheap of course.