Selling car with frame damage

My father has recently bought a car
from a private seller. When asked
about the car he said that it is in
good shape and will pass inspection.
When we took it to get inspected
turns out there is frame damage and
it will not pass inspection. However
the seller owns his own repair shop
and slapped an inspection sticker on
it so he was able to drive it. I was
wondering if he can legally do this
and if there is anything we can do
about it