With the concepts of firearms in Pokemon, we cannot look at the games or anime for a few reasons. First off in the games and anime, they are based around children and those types of characters wouldn’t be involved with the types of characters who would own/use guns. The world in a sense, has been bubble wrapped, to the point where dangers like that wouldn't be an issue. Secondly, we have to remember that this world is marketed toward 10 year olds so things like Guns and dangers would be avoided by the developers.
So if determining whether or not guns exist, cannot be done by using the games or the anime as primary sources, then how can we figure this out? Well we need to look instead on how they would be used. We already know that the technology is advanced enough in the Pokemon realm to allow or the creation of guns, as we see more advanced forms of weaponary throughout the anime, like Bakzookas and tanks. And like Kol pointed out, guns would be useless when compared to the strength of Pokemon, any day. Except for the simple concept that guns are at a base if you will. They cannot grow stronger nor weaker, while Pokemon can. And there is also the concept that Pokemon, aren’t always these massive powerful creatures but need to be trained. So without a gun or weapon along those lines, you would need to train a pokemon a whole bunch for the simple act of killing a single person or entity. Not very efficient. A gun would be a Pokemon that needs no training to be deadly. ‘
So why don’t Team Rocket members, pull out a gun and shoot a trainer in the head during battles? Well this is where things get a bit more interesting, in my opinion. We must think of the types of people who would use guns instead of Pokemon. In the picture above, it shows an elderly man pointing a revolver at Ash Ketchum’s head with it ready to fire (unfortunately he never does, ruing he dreams of many). Now this man, if memory serves me correct, runs the Safarai Zone and he would protect the Pokemon inside from outside threats. So maybe he wouldn’t use Pokemon for 1, to keep the pokemo inside feel safe and keep any other species that didn’t belong, out of the safarai zone (introducing other species can be bad for natural species of that habitat, as they would play the role of an invasive species) and 2 to keep the Pokemon inside, away from fighting. So we can conclude that the people who use guns would actually have guns as an alternative to Pokemon.
And now, I’m gonna answer the Team Rocket shootout part. Guns, like I said previously, are at a base level. So if both sides have guns, then it might as well be a 50/50 chance for victory. So if evil teams use Pokemon, which can outclass guns, than so would the police. So then it would stick to which Pokemon is stronger. And if we look at these leaders they are all top notch, implying that they will have a better win percentage with these leaders on their side, with those stronger Pokemon.
So in conclusion, guns do exist in the Pokemon world, but are obsolete. Not just because Pokemon outclass them, but because guns are at a base strength level, that with guns being the only weapons, the sides are more balanced. And then the only people who would use guns would be those who wish to fight, without using Pokemon.
