WhatsApp is not subject to the Brazilian justice system, it does not have to answer to Brazilian law.

And that tends to make Brazilian judges quite angry and thus they do the only thing they can do. Which happens to be blocking WhatsApp (the only real weapon that works against WhatsApp they have)

Sure, which is clearly far from legal. No wonder it is quickly overturned every single time, like now, lasted what, 12 hours?

Five hours this time.

Then Brazil doesn't have to allow them to operate in their country.

They don't operate in Brazil, just like other millions of websites. Do you think every single website that wants to serve content to someone in Brasil should have a subsidiary in the country?

That's not how the internet works.

Having written a letter to the Brazilian Congress about (almost) this very issue (in connection with the CPI-Cibercrimes inquiry), I think some Brazilians may be surprised to know that the U.S. does not require ISPs to block connectivity to third-party foreign Internet sites that facilitate violations of U.S. laws, directly violate U.S. laws, or ignore U.S. court orders, as long as the ISPs themselves have no relationship with the sites. In fact, a proposal to begin doing so in copyright cases, known as SOPA/PIPA, was extraordinarily controversial in the U.S. and was effectively defeated. The U.S. legal system generally appears to accept that ISP blocking of third-party connectivity is simply not an available remedy, even in "clear" cases of legal violations.

That means that it is not universal or obvious that this kind of blocking would be practiced or accepted. (For example, if a Brazilian company ignored a subpoena from a U.S. court, there would not be a legal basis for the U.S. court to order ISPs to prevent Americans from accessing that company's services.)

Some portion of Brazilians think it is "obvious" that a government would never allow its citizens to access Internet services that allow or commit violations of local law, or are simply not subject to local jurisdiction at all. But it's not obvious at all.