|This article is written from the Real World perspective|
It is unclear who enacted the embargo, but it is commonly believed to be either DC Comics or Warner Bros. The reason Warner Bros. supplied is that with the coming of The Batman, children (their target demographic) would be confused to see two different versions of the same characters at the same time.
This reasoning does not explain everything associated with the embargo. A number of Batman characters reserved never saw use in The Batman (i.e., Two-Face, Ra's al Ghul, the Scarecrow, and the Mad Hatter), most likely because they were to be used in the Christopher Nolan movies (except the Mad Hatter). It also does not explain why other heroes were also banned. Nor does it explain why Batman himself was allowed to continue appearing in Justice League Unlimited. These questions present (but by no means confirm) the possibility that there were other reasons involved in the ban.
Words from the creative team
|“||I don't see the Bat-embargo lifting anytime soon but, to tell you the truth, as much as I [...] love those characters, I don't really miss [them] all that much. It's not like we don't have tons of other interesting characters to play with. If I were doing an actual Batman show, and not allowed to use those characters, yeah, that'd be pretty galling, but Batman's only one ingredient in the Justice League's brew. The Bat-clan aren't really essential in any way to the current show [...] I mean, did you guys miss Ra's al Ghul in "Wake the Dead"? Would "The Return" have been a better episode if Nightwing were in it? I know your answer would be yes, but seriously, I don't mind a break from those characters after working on them for so many years.||”|
— Bruce Timm on Toon Zone
|“||All I know is [that the Batman characters] they’re off-limits for the foreseeable future. If it changes we'll use some of them but I wouldn’t count on it happening soon||”|
— Dwayne McDuffie on DwayneMcDuffie.com
Implications of the Bat-embargo
- Characters exclusively reserved for other TV shows and movies in development or production include most characters from the Batman comics due to the "Bat-embargo" that reserved those characters for the new Batman cartoon The Batman and the new Batman movies. Only Batman could appear, although Nightwing made an uncredited cameo as a silhouette atop a building in Blüdhaven in the episode "Grudge Match".
- Originally, Barbara Gordon was to appear in the Justice League Unlimited episode "Double Date". The episode would have her getting injured during a case as Batgirl. Since Bruce forbids her from participating, she would recreate herself as Oracle, and get in touch with Black Canary and Huntress to finish her case. Neither of them would meet her in person. Due to the Bat Embargo, the story was changed to include Green Arrow and The Question instead.
- The introduction of the Legion of Doom in season three of Justice League Unlimited conspicuously lacks the major Batman villains the Scarecrow and the Riddler, both of whom were part of the original Legion of Doom in "Challenge Of The Superfriends".
|“||As you suspect, many Batman characters are unavailable for JLU, at least for the time being. It's only been a problem a couple of times [...] I wanted to use Hugo Strange [...his appearance in "Doomsday Sanction"] was to set up a later appearance. The later appearance won't happen now.||”|
— Dwayne McDuffie on DwayneMcDuffie.com
- The "Bat-embargo" started around the middle of the second season of Justice League Unlimited, seeing as Hugo Strange was featured in "Doomsday Sanction" but was unavailable onward. Dwayne wanted to use the character later in the second season, presumably for the interrogation scene in "Question Authority", but couldn't do it due to the embargo. His role was later taken by Doctor Moon, a brain surgeon who is the go-to villain of the DC universe when 'evil' brain-washing is required.
- No more Joker appearances, which was unusual, since he had appeared prominently in earlier seasons.
- The Penguin or other Gotham City influential mobsters like Black Mask, Two-Face, Rupert Thorne or Scarface did not appear in further episodes. According to Bruce Timm, after his redesign of the character for The New Batman Adventures, the Penguin started to have a very influential role as a kingpin for Gotham City underworld, working behind the scenes a la Lex Luthor. His power and position was especially shown when he was last seen, on the Batman: Mystery of the Batwoman movie.
- During the "Batman Adventures" (2003–2004) story arc, the last comic book based on Batman: the Animated Series, all the rogues evolved. The Penguin became mayor, Black Mask and Red Hood made their first appearances, and Poison Ivy, Mr. Freeze, Talia, and the Riddler had also major changes in their lives. Although the comics based on the DCAU stories are not canonical to it, the producers have often adapted some of the plots to the actual DCAU in the past, especially when Timm was involved in the comic's production, like in this case.
- The long-anticipated reappearance of Ra's al Ghul and his related League of Assassins, which is already part of the DC Animated Universe continuity, wasn't possible.
- Characters created for the DCAU, like Harley Quinn, and then incorporated into the DC Comics mainstream were included in the embargo.
Many fans were unhappy with this policy and expressed their discontent through petitions   intended to reverse it, or at least to convince Warner Bros. to allow the inclusion of Batman's archenemies the Scarecrow and the Riddler in the Legion of Doom. However, it had no effect, because the show was ended before this ban could be lifted.
End of the embargo
Many web articles that refer to the Bat-embargo were last updated in the year 2005, meaning very little current news is available. The use of formerly banned characters in Batman: The Brave and the Bold suggests that the ban has been lifted or altered. However, with the closure of Justice League Unlimited and no other current media that would make effective use of these characters, details have not been widely circulated.
- The Aquaman embargo:
- DC Comics has asked the Justice League Unlimited staff not to use Aquaman or any of his family or characters, this is due to the recent appearance of the character on Smallville, a storyline featuring the character on the television series Entourage, and the announcement of a Smallville-esque "Aquaman" spin-off series. A pilot episode, "Mercy Reef", was filmed, but it didn't get picked up by the network.
- According to Television Without Pity, producers changed Black Manta to Devil Ray and removed Aquaman from "To Another Shore" because the rights to Aquaman were no longer available.
- The Wonder Woman embargo:
- Bruce Timm admitted in an interview shown on the first season DVD that he initially ran into some legal issues once he told Warner Bros. that he wanted to use Wonder Woman for the series. He was eventually successful in being able to use the character for the show, but later other animated series ran into similar road-blocks preventing the use of both the Wonder Woman character as well as established Wonder Woman supporting characters.
- The other heroes:
- The same happens with some of the rest famous superheroes not seen on the show. There was a list of superheroes with "rights-available".
|“||I think (Nemesis) was on a list of 'rights-available' guys that DC gave to us. And he is a unique 'type,' so we said, 'What the hell, put him in the show, we need bodies.' I would much rather have had Phantom Stranger, Spectre, Blue Beetle, etc, but they were off-limits for whatever reason.||”|
— Bruce Timm on DrawingBoard.org