My own post here covered that. Nintendo owns the trademark to the name “Pokemon” as well as the trademark to every single character/names of the Pokemon themselves. It’s quite clever on their end.
Anyway, to @AllianceOfficer 's question on “how can they one-up ABK and get away with it?”, my answer is probably boring but I’d say they cannot. They bought the biggest third party publisher. The only upwards direction is buying out a competitor which is off the table lol.