[US/UM] Can you tell if a pokemon is legit or not?

[Black Waterfall]

(Nov 24, 2018, 01:16 AM)Honest Doodle Wrote: Recently i just got a Shiny Mew off of the Wonder Trade, now to be 100% honest, i do not believe in any way that this mew is legit... That was untill i started researching it, where it was met/caught, the pokeball it is in and what not.  Either the person that cloned it did a VERY good job covering their tracks, or someone was giving up on the pokemon game and started to WT their pokemon away.

@Honest Doodle I'm pretty sure mythical Pokemon cannot be legally wonder traded unless their ribbon is removed, so it should be an edited Mew at very least.

Concerning the more general question about legality, there used to be a very thread by @gkh1997 explaining what is legal and what is not for every generation, but I can't find it anymore.

http://pokemonforever.com/Thread-DISCUSS...#pid253863 

I think that was the link for the thread, but it seems to be broken now. Maybe someone can help?