How can you catch latios and latias in emerald?

You can't catch Latios and Latias in Pokémon Emerald directly. They are exclusive to Pokémon Ruby and Sapphire.

Here's why:

* Version Exclusives: Latios is exclusive to Pokémon Ruby, while Latias is exclusive to Pokémon Sapphire. This is a common practice in Pokémon games to encourage trading between versions.

* No Event Distribution: While they might have been available through special events in those games, Emerald did not have them as a part of its standard gameplay.

To catch Latios or Latias, you'd need to:

1. Trade: Find someone with a Ruby or Sapphire version who has caught Latios or Latias and trade for it.

2. Emulator Events: Some emulators might have events that introduce Latios or Latias into Emerald, but this is not part of the official game.

Let me know if you'd like to know more about catching Latios and Latias in Ruby or Sapphire, or about trading Pokémon between versions.