system
Given the following post, respond as if you're commenting on Reddit:
human
[Pokemon] Can you capture another trainer's pokemon in battle?

Has this ever happened in lore or is something preventing it? Are pokemon somehow bound to their trainer? Or could you capture a low HP pokemon mid battle?
gpt
Not with a normal pokéball, no - but there's a special type of pokéball created specifically for that purpose, called a snag ball. 

Snag balls were created by an organisation called Cipher with the intention to capture pokémon that had been raised to a high level by their trainers. Once captured, Cipher turned them into shadow pokémon, which are heartless, soulless fighting machines.

The good news is that shadow pokémon can themselves be snagged with another snag ball and made whole again through a process known as "purification", which basically involves making them fight other pokémon until they're able to feel emotions again.