Harmony Gold own the rights to the Macross designs in the U.S.; it doesn't matter that they didn't create those designs. It's similar to how Hasbro owns the rights to the likenesses of all the original G1 Transformers, even though early G1 toys were made by other companies like Takara (re: Diaclone). If someone in a Hasbro market country were to counterfeit or use the likeness of an early G1 Transformer without Hasbro's consent, then Hasbro would be within their rights to take legal action against that party.
Here's an admittedly simplistic analogy: you didn't build your car. But you purchased your car and are its legal owner. If someone were to damage or steal your car, it would be you who would take legal action rather than the manufacturer.
Having said that, I do agree that the idea of just IP squatting is a bum-hat thing to do.Jetfire's always been a difficult toy in terms of legal issues though. The G1 cartoon/comic design had to look really different from the toy to avoid legal conflict with Harmony Gold, and the G1 Jetfire toy was never released in Japan since it would've meant a conflict between Takara and Takatoku Toys. The Classics/Henkei toy was a hybrid approximation between the original G1 Jetfire toy and the cartoon/comic model (which I reckon is a nice compromise).
But even if Hasbro were able to secure rights to the Jetfire design, all reissues are done by Takara(TOMY) first. Hasbro just brings them over after Takara does it. We've never seen Hasbro reissue a toy that Takara hasn't in the past 13 years. So IMHO the argument that Harmony Gold is somehow preventing a G1 reissue from possible is a fairly moot point since Takara would never have been able to do it regardless of who owns the rights to the designs outside of Japan.