The need for law enforcement authorities cooperating with private companies is not new. Personal data retained by private companies can be necessary for the purpose of preventing, detecting, investigating and prosecuting criminal offences. Besides issues with purpose limitation and retention periods, companies are developing products that aim to protect citizens’ privacy and data by using encrypted soft ware and building personal servers. Such products are good news for law-abiding citizens who are concerned with the protection of their personal data and privacy. Such products however also protect data that are part of criminal offences such as child sexual exploitation and terrorism, making it difficult for law enforcement authorities to access these data for the purpose of preventing, investigating or prosecuting these criminal offences. Thus, essential questions are how law enforcement authorities should approach this additional challenge on the one hand and how legislators should react to this on the other hand.