According to The Hollywood Reporter, the Axanar team’s lawyers are demanding Paramount specify which of the many, many Star Trek copyrights on the books that they’ve violated, and who, exactly, owns them—a question made nebulous by the franchise’s long history, and the vast array of mediums (TV shows, movies, video games, cartoons, comics, Dr. Beverly Crusher’s Patented Ghost Sex Candles) it exists in. Essentially, they seem to be claiming that there’s no singular copyright on “the expanded Star Trek universe”—which, incidentally, is probably why Disney nipped this sort of thing in the bud the second it snapped up Star Wars—just a collection of thousands of different rights, smeared across different corporations by various sales and mergers, and that if someone’s going to sue them, they deserve to have which elements of it that they’ve supposedly violated defined.
It’s not entirely clear whether this approach will hold up in court, or if it’s just a stalling tactic from the filmmaking team. But it does suggest that the Axanar producers aren’t willing to immediately roll over just because CBS pointed its lawyers at them (or, possibly, that they just want to inflict their own need to categorize, catalogue, and list every single aspect of Federation and Starfleet lore onto their legal opponents, in some form of horrific karmic revenge).