The report [PDF] opens up with this statement:
It is in the national interest to encourage the use of strong encryption. No one we interviewed in law enforcement or the intelligence community disagreed with this.
The disagreement comes when law enforcement is prevented from pursuing investigative leads because of encryption. According to FBI Director James Comey and Manhattan DA Cyrus Vance, encryption is already a huge problem for law enforcement and will only get exponentially worse in the next few years. The CSIS report rebuts both of these statements.
While encryption use is growing rapidly, the share of traffic that is both of interest to law enforcement and unrecoverable is still relatively small. Most companies use encryption that allows law enforcement agencies to recover plaintext data. Most e-mail, if it uses encryption, also allows for recovery. Currently, an estimated 18 percent of global communications traffic is end-to-end encrypted. It is estimated that 22 percent of communications traffic will be end-to-end encrypted by 2019.