>The use of foreign-language cards have been known to create time delays and and confusion at high-level Premier Events, where significant prizes are on the line. However, as the Pokemon TCG is an international game, concessions must be made to help accomodate markets where multiple languages are more common. Players are restricted on which language cards they can use, based on the country where they are playing. Any other languages are considered foreign in that country or region.
Here's a list of countries / regions and the languages they are allowed to use:
- Canada: English and French
- Europe: English, French, German, Italian, Spanish, and Portuguese
- Mexico: English and Spanish
- South America: English, Spanish and Portugese
- United States, Asia Pacific and South Africa: English
Players are not permitted to use foreign cards at Premier Events.
>For the Pokémon TCG World Championships and the Last Chance Qualifier, players are
permitted to use cards that are legal in their home markets. Reference cards are not required
for the Pokémon TCG World Championships or the Last Chance Qualifier.
So if you happen to be from Europe, yes you are allowed. Otherwise no.
Source, on page 5, 1.8, Foreign Cards.
Hope I helped!