The Joker and his men were plotting to poison the people of Gotham City in the streets, so Batman tried blowing them up before the parade ever happened. There was no indication that he wasn't in the Batmobile. The Joker was already gone, so he went and got the Batwing.
Okay, let's explore that a bit.
First, while I express some views on how things would play out in a legal sense - that's not me trying to definitively state what the law would do - only a court can do that. I'm not a judge. Just saying.
Second. The big problem that Batman has is that as a civilian he's not lawfully allowed to kill other people - except under certain circumstances, and those have to be proven in a court. I see where you're coming from, in terms of Batman acting to protect Gotham, rather than himself - and you've got a point.
I suppose if you treated the Joker not as a criminal but as a domestic terrorist, preparing for an attack against Gotham, and Batman was a police officer, soldier or other government agent - then a preemptive strike against Axis Chemicals would probably be okay (he might even get a medal).
So, keeping in mind that Batman is a civilian - in terms of blowing up Axis chemicals to prevent the poisoning of Gotham, Batman has to rely on self-defence, because civilians generally aren't authorised to use force like that (the main exception being in time of war).
What Batman'd be arguing is
self-defence/defence of another and his argument would go something like " I killed those goons to protect the citizens of Gotham from being poisoned by them" the question for the Court would be about evidence. Without pretty solid evidence that that was the case, he'd be in serious trouble. I mean, that kind of argument would be a tough one even for the actual police to rely on, without a lot of evidence. How much evidence did he have ahead of time ? Well we're not 100% certain from the movie - but let's say he probably had a fair bit, although a lot of that he's blown to bits.
So he's got evidence of the plan to poison Gotham. Here's the other thing about self-defence. Usually, to successfully say you were acting in self-defence and have a court excuse you from using force, injuring or killing a purported attacker you need 2 things:
[*]- a belief that you or someone else was in immediate danger
[*]- under the circumstances of that belief you only used reasonable force.
Different courts weigh up the degree of reasonable force differently (e.g. if you believe someone is going to punch you, then chopping off their head probably isn't going to be considered reasonable force). In this case, if the thugs are going to poison all of Gotham, then blowing them up might actually be reasonable force......unless another alternative existed (as in giving them a ten second warning to get out of Axis Chemicals before the explosion ). Who knows ?
For me, the problem is more about the immediate danger requirement - sure he believes that the Joker's going to poison Gotham but how immediate is the threat ?
There are different views on how imminent or immediate the danger has to be, in order to succeed with self-defence as a defence.
It is true that sometimes a court (or a jury) will accept that if you are confronted by an attacker, and
you hit them first because you believe they are going to attack you. But that's sometimes. Again you need pretty solid evidence to back that up.
Sometimes that immediate danger requirement can be stretched. Like if the Joker was about to launch a poison gas missile (from Axis chemicals) and Bats blew up Axis Chemicals to stop him....that's pretty imminent. Again it would be much easier for a police officer to make such an argument (think of every police officer who's shot an offender who was threatening him/her with a weapon) - because remember, as a vigilante Batman's already operating outside the law.
In terms of immediacy, generally the courts take a very short-term view.
In a case down here in 1990, a woman who suffered regularly from domestic abuse killed her husband in his sleep, and asserted self-defence. He had threatened to kill her and her sister before getting drunk and going to bed. At trial, the judge decided that there was no way she was in immediate danger, so killing him can't have been reasonable force (so her self-defence defence failed and she went to prison) . This was upheld on Appeal - but there's been a lot of work on domestic violence since then, and I'm not sure it would have been decided the same way today. However, what it does show is just how immediate some judges expect the danger to be - the law is crazy sometimes.
So going back to Axis Chemicals. Well, maybe a court (or jury) might accept that Batman believed the citizens were in danger - but again would the danger be immediate enough at that stage ? Who knows ? Of course, the goons who died at Axis Chemicals weren't going to attack the city immediately, because as you say, the Joker was already gone (already in his helicopter - from which he taunts Batman) they then have to get the balloons into the city and deploy them. I'm not so sure the threat would be immediate enough, but that's just me.
Of course, this raises another question. When Batman strafes (and kills the Joker's goons) from the Batwing, he's already removed the poison balloons - and the goons are firing over the crowd's heads, not into the crowd. It looks like Bats might have a tough time justifying opening fire there too - because the level of immediate danger is lower.
Check it out
https://www.youtube.com/watch?v=Udvhwg_sd1k
Now, I'm also not saying that Batman's actions aren't morally justified, just that if he had to defend them in court, he'd have a tough time (although who knows what a jury will do ? A jury could find that he was totally justified). What I'm saying is that there's a big difference between moral and legal justifications.
Finally, don't get me wrong I love Batman '89 and I think blowing up Axis chemicals works within the story (even with a Batman who supposedly doesn't try to kill people). What interests me is the
legality of comic book movies, and how real world law would apply - thank goodness it doesn't, because then the stories would probably become a lot more boring and less action-packed. But, it still interests me.
Oh PS-
As for Batman not being in the Batmobile - I think there's a very good indication that Batman wasn't in the Batmobile when he bombed Axis- check out the clip below. After blowing up the plant the Batmobile drives out and right up to Batman who stops it with his remote control (something he demonstrated he could do, earlier in the film). Have a look from about 1:00 onwards.
https://www.youtube.com/watch?v=lUPudZd3oI4
Cheers.
