IIRC, US copyright law includes the ambiguous words "slavish copy" with reference to something that would not be copyrightable. For example, the Vatican sold copyright to the imagery that is the restoration of the Sistine chapel roof - self evidently a "slavish copy" by design! - to the company that paid for the restoration, so they could have exclusive rights to sell/license reproductions of this restored imagery. They've never taken anyone to court, (quite possibly because their case is wobbly), but they do assert their rights to this work and try to get people to buy licenses accordingly.