Is it illegal to re-badge a car?

If I were to take a Chevy Tahoe, replace the grill with a Cadillac Escalade grill, replace the taillights with Escalade taillights, and put Cadillac badges on the Tahoe, and put an ad out for it claiming that it's a Cadillac Escalade, would that be breaking the law? I was at a dealership recently that seems to be doing something similar to this.