Upvote:3
Under EU 261 rules, the operating airline is responsible for compensation claims if you presented correctly and with valid documentation, in this specific case 'denied boarding':
- If boarding is denied to passengers against their will, the operating air carrier shall immediately compensate them in accordance with Article 7 and assist them in accordance with Articles 8 and 9.
How that compensation claim is handled internally between contracted parties is outside the scope of the EU regulation.