Some commentators, such as technology entrepreneur Declan McCullagh and law professor Glenn Reynolds, have criticized Twitter's suspension and ban policies as overreaches of power. In January 2019, Twitter formally provided information on instances where governments have attempted to utilize Twitter for 'foreign information operations'. In addition to community guideline policy decisions, the Twitter DMCA-detection system and spam-detection system are sometimes manipulated or abused by groups of users attempting to force a user's suspension. They are told only that their accounts will not be restored, and they are told which of Twitter's rules the company claims were violated. Users who are suspended from Twitter, based on alleged violations of Twitter's terms of service, are usually not informed which of their tweets were the cause.