I know in some non-US countries, WhatsApp is the default way of communicating (like SMS is in the US). Is that true in the UK? That could put significant pressure on the government
I don't know this is a fight the UK government can win. Does anyone else remember that the American government tried to ban encryption (back in the 90's I think it was)? They eventually had to give up because people just downloaded encryption products from the internet and used them anyway.
Such rules are not unusual for physical objects - why sell your enemies or even potential enemies the rope they will hang you with? But for encryption it doesn't make sense because it's just information, and unlike physical objects, after writing is invented humans can trivially reproduce information, so too bad.
Eventually they whittled the "export license" step to something like a form letter Fax and IIRC Mozilla had a process where you raised a Bugzilla ticket, that caused the appropriate fax to be filled out and sent, so that was part of the release process, making it as painless as possible to comply with the stupid law.
(And now it's gone altogether)
And then came the Clipper Chip...
https://www.theregister.com/1999/01/15/france_to_end_severe_...
WhatsApp can pretty clearly know if a user of the app is in the UK based on their account’s phone number country code and GeoIP. So if they wanted to comply by pulling out of the UK completely they’d probably have to make some attempt to disable WhatsApp messages for those users they’re reasonably expected to know with some confidence are located in the UK.
But as others have said, this all just seems like posturing that’s unlikely to become law.
It comes down to jurisdiction. If you don't have it on the default marketplace for the region, and don't have a physical business presence in the region, it can be argued, you've done enough and aren't subject to the jurisdiction and are not doing business there.
That users may bypass and side-load your application is immaterial. If a user in the UK uses a US based VPN, they can also still use the app even if you added IP blocking, and IP blocking in and of itself is less than perfect often subject to false positive/negatives, and best to be avoided.
Recall that in the US there is no explicit right to privacy. You might be able to make a 1A argument that manually encrypting a message is itself a speech act, but the government could theoretically ban the distribution tools like Signal and argue they have the authority under the commerce clause, which stands on a equal Constitutional footing to the 1A.
I don't think this is likely, but I could easily see it being offered as the justification to honor a UK ban.
2) I'm not making any claims about it being desirable or effective, I'm just explaining what 'exiting the UK' means or what they'd be required to do. The crown won't sue a foreign company because a citizen found a way to workaround it not being available here - that would be like criticising the manufactuter of an illegally dangerous electrical item only rated for and sold in 110V markets that someone imported.
I think it's more of a "don't want to know" than anything, in which case it's their own problem IMO.
P.S. I'm always shocked how people suggest "just use Signal" or something, it's really not up to me what to pick what to use at all, but up to the people I'm trying to connect with. It seems like a very difficult concept for the "just use Signal" crowd to grasp.
Switching costs are free.