This is due to the addition of Meta AI in WhatsApp [0].
Unsurprisingly, data egress to third parties is a major security vector - especially for mission critical jobs like working in the House. MS apps incorporating Copilot have faced similar blocks as well.
This requirement for data stewardship is called out in HITPOL8 as well [1][2] (the AI tool standards set by the House CAO).
Signal would be the obvious choice here - open source, no AI integration, minimal metadata collection, and recommended by security professionals for sensitive communications.
Wouldn't this be pretty easy to roll your own? You could set up different servers like Molly does. Or you could just recompile the app. Or you could force link it to a desktop session? Just spitballing here
The article as well as HITPOL8 [0][1]. WhatsApp has been blocked for the same reason Deepseek AI (the Deepseek app) is blocked - "Stewardship of Legislative Branch Data".