Reasons teams get locked in Yahoo Fantasy
In an effort to keep the gameplay fair and enjoyable for everyone, teams can get locked based on their behavior. Locked teams have certain privileges revoked -- such as adding or dropping players, editing their roster, and posting to League Chat.
Locked teams in Private Leagues
Private League commissioners have the authority to lock any team (at any time) without warning. If you've been locked, try to contact your commish via League Chat or by email (if those options are still available). We won't interfere in Private Leagues for any reason in any way. There's no exception to this policy and encourage you to pick your private leagues carefully.
Locked teams in Public and Public Prize Leagues
A manager in a Public or Public Prize League (formerly Pro League) found to have violated the Terms of Service or Fair Play & Sportsmanship guidelines, among other codes of conduct, may be disqualified from the contest. In addition, Public Prize League managers could be ineligible to win a prize, as per the individual fantasy sport's official rules:
We appreciate your interest in remaining active in your leagues. However, any actions taken in response to a violation of Terms or Fair Play & Sportsmanship are final.