Is This A Legal Way To Set Up Your Bike Rack In Idaho?

I was driving into work this afternoon and noticed something not uncommon throughout the Treasure Valley; A rear-mount bike rack on the car in front of me  But, is it legal to do it this way?

I noticed this driver in front of me had blocked their license plate with the lower portion of the rack, and if I understand it correctly, that could be a big ticket.

Have you had any experience with this?  What do you do if your rack would block the plate?