I am Brazilian, I am in favor of privacy and access to strong crypto for everyone, I think most judges don't have a clue about how WhatsApp works.
Having said that, you don't answer a Court Order in a country where you operate and have offices over e-mail, in a foreign language, asking for details about the ongoing investigation (in English, please)!

Quote from the e-mail, contained in the decison:

"If possible, please provide responses in English as that will significantly improve our ability to analyze and process your request in a timely manner.
1. Is this a criminal matter?
2. What organization is conducting the investigation (Federal Police, Civil Police, Prosecutor's Office)?
3. What is the nature of the crime being investigated (corruption, drug trafficking, gun violence/homicide, child exploitation, terrorism, etc.)?
4. What are the specific WhatsApp accounts that are the target of this legal process (including all applicable country codes)?
5. What data are you requesting for each of the targets listed above?"

Unquote

The reason the appeal was granted is not simply because the higher court disagreed with the judge's decision. It was granted because it was done in writing, by lawyers, respectfully and in Portuguese. It is that simple!

I read and enjoyed "My life as a quant" , by Emanuel Derman.