It's important to distinguish between us and the party that you might be engaging with when you visit a website. If a law enforcement entity came to Mozilla and said that it needed information about someone's web-browsing activity, we largely would not be able to satisfy that request. It is data that we do not have and do not collect. There is the cross-site tracking I mentioned earlier, which happens sometimes by third parties using Firefox. Those third parties might have that data, and a law enforcement entity would have to go to them to get it.
On April 26th, 2018. See this statement in context.