No.
You are not allowed to catch other trainer's pokemons on any of the Pokemon games. You may only catch Pokemon from the wild or receive them through other means (events, game corner, eggs, etc.)
u catch it like any other trainer.
train him or go catch all the other pokemons
You can catch more legendary pokemons on platinum. So you can catch more on Platinum, then the other games :)
It is a wild Pokemon, so no, it does not belong to a trainer. You can't catch other trainer's Pokemon.
You can't. You could obtain the other trainer's Pokemon in only Pokemon colloseum or XD.
First you have to get the action replay. But both action replays can ONLY connect to Pokemon Pearl, Diamond, and platinum. So if you want to connect to Soul Silver there is a place to add it. You can add all Pokemon games. So to catch trainers Pokemon you need the action replay. Then go to a trainer who you never met then he will battle you. After try to use the right ball to catch the Pokemon. Then automatically the battle will stop. That is how you catch trainer's in Diamond/Pearl/Platinum or any other. Bye for now. And your welcome for my answer.
go to lillycove city and go to the SAFARRI ZONE AND A LOT OF OTHER POKEMONS>
a master balls can unfailingly catch and Pokemon unless the Pokemon owned by another trainer and it is best not to waste them on weak Pokemon easy to catch and use them on dialga and other legendary Pokemon you only have one chance to catch in the game.
A gastradon in the pokemon diamond, is a pokemon. He can evolve into different pokemons' and also fight other pokemon. He eats leaves, vegetables, and fruits.
You can't catch other Trainer's Pokemon. It is not an intentional feature in the website.