This just made me realize that for the majority of people that use their ISP's router, there is effectively an easy backdoor (with a firmware update) into their

This just made me realize that for the majority of people that use their ISP's router, there is effectively an easy backdoor (with a firmware update) into their private LAN. What would stop a government agency (w/ or w/o a subpoena) from requesting the ISP provide access to your local network w/o your permission, accessing resources you otherwise thought were secure? Or really, any malicious entity that can figure out how-to forge the certificate required to do this.