How should this be enforced? Mullvad doesn't even know where the customers are from (if they pay anonymosly), so they can't check if the legislation applies to a specific customer.
Also (and I'm not trying to legitimate such law projects), age verification without identity leak is possible. The government needs to distribute a ZK proof system linked to ID cards which creates a signed proof including "holder of the ID is over/under 18" and a service-dependend pseudonym (to prevent repeating the proof for other users).
Geheimtipp: sehr wenig bewegliche Sachen besitzen