If anyone thinks that some sort of master keys for law enforcement to decrypt your traffic is a good idea, I would point you to the TSA's system. Nearly all their superkeys have been reproduced by others outside their organization.

As someone whose fingerprints were lost (by OPM, a US government agency) to the Chinese Army several years ago, I do not trust the government to adequately safeguard the security keys needed to intercept my banking, my book purchases, and the videochats that I have with my kids and grandkids.

Also, if you're in California, Diane Feinstein believes that giving national security and law enforcement agencies this kind of access is vital to prevent perverts from exploiting children. Remember that when voting time comes around.

The police can use good old fashioned police work to find such people, obtain a warrant to plant observation devices, then collect the evidence needed to prosecute.

The national security folks can probably already crack any encryption you or I might use, but not millions of messages at once, so they have to learn to prioritize messages involving people who show signs of foreign influence or those who would do the most damage if they turned out to be spies / terrorists.