It is "easily", because current commercially available "firewall" appliances include that kind of capabilities. Just a few clicks, install a CA certificate, add a logging endpoint, done. Certain regulated industries like finance and medicine are required to use those. All chats are instantly intercepted and logged.
And the way to spy on people via a certificate authority is exactly as described, you get a CA that signs your man-in-the-middle certificate for a website you do not own. Then you MitM that traffic using that certificate, while still getting a green "lock" icon.
With current WebCA certificates, certificate transparency does help a little to detect such MitM certificates, and some CAs have actually been caught red-handed. There are processes to punish or remove such CAs. However, this law would also prevent such actions, thus making it impossible to prevent any future malfeasant CAs.
About an example MitM certificate case and removal, see the DigiNotar case:
https://blog.mozilla.org/security/2011/08/29/fraudulent-goog...
For more about how certificate transparency works see http://nil.lcs.mit.edu/6.824/2020/papers/ct-faq.txt