I will assume that imitating Reagan to sell X products (that are not insulting the to the memory of Reagan) would be "ok". But Reagan is dead, and I don't feel

I will assume that imitating Reagan to sell X products (that are not insulting the to the memory of Reagan) would be "ok". But Reagan is dead, and I don't feel that using a voice similar to his (or Clinton's who's still alive) removes bread from their table. If everyone deliberately starts using a voice 'like' Johansson's, or the image 'like' Johansson's, that would steal the bread from her table. I don't know if there are laws/cases covering 'lookalikes' but it's kinda like that.