Yes, as Species Clause bans Pokemon with the same Pokedex number.
>Species Clause - A player cannot have two Pokemon with the same National Pokédex number on a team.
For example, using a team with two Koffing would break this clause.
Using different formes on the same team, such as Rotom-W and Rotom-C, also breaks the clause since they share the same Pokédex number (#479).
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