The US supreme court's unanimous 9-0 opinion this week requiring police to get a warrant before searching your cellphone is arguably the most important legal privacy decision of the digital age. Its immediate impact will be felt by the more than 12m people who are arrested in America each year (many for minor, innocuous crimes), but the surprisingly tech-savvy opinion from Chief Justice John Roberts may also lead to far more protection than that.

Roberts's analysis of the current state of the digital world in his Riley v Wurie opinion is was so thorough, and so sweeping, that I'd be willing to bet you won't find many privacy and technology cases going forward that don't cite this one.

From phone tracking to NSA snooping and beyond, here's a look at the domino effect.

1. Cellphone location information: not 'just metadata' anymore

One of the most contentious issues in courts high and low right now is the extent to which your cellphone location information should fall under the Fourth Amendment's protection against unreasonable search and seizure. Whether you're on a call or not, your phone emits a signal to cell towers that pinpoints your exact whereabouts, 24/7. And the cops believe – as they do for most things digital – that they can get that information without a warrant. Two appeals courts have, sadly, agreed with them, but two weeks ago, the 11th Circuit Court of Appeals issued an important decision: yes, your location information should be protected. The 11th Circuit relied heavily on a concurring opinion by Justice Sonia Sotomayor in a case involving GPS trackers from 2012 called US v Jones.

In this week's supreme court case, Roberts approvingly cited and quoted from that Sotomayor opinion when explaining just how sensitive the location data emitted from your phone can be – even though he didn't join Sotomayor's opinion at the time. That's a big deal.

Sotomayor's concurrence that "a precise, comprehensive record of a person's public movements ... reflects a wealth of detail" isn't binding law, and neither are Roberts's comments on the sensitivity of location information. So the supreme court isn't necessarily endorsing warrants. But there will be a ripple effect of citations every time the government argues that your location info is "just metadata" and shouldn't count as a search. And given that Riley was a unanimous opinion, it might be more of a tidal wave than a ripple – and phone companies may not have to hand over our data to the authorities with little to no oversight for too much longer.

Oh, and Stingrays, those fake cellphone towers cops have been using to vacuum up the cellphone information of entire neighborhoods? Those are in trouble, too.

2. The NSA: 'reason to be nervous'

Inevitably, everyone's going to wonder what this week's cellphone decision means for the future of mass surveillance by the National Security Agency. At first blush, it doesn't – at least not directly. Roberts adeptly sidestepped any questions about collecting pure phone records, either individually or en masse.

But if you read carefully, Roberts did throw a wrench into the NSA's main defense for what it does: self-policing. The NSA's argument has always been essentially this: we don't need court oversight over our massive surveillance machine because our internal privacy controls are so good.

Roberts, however, ridicules this theory in his Riley opinion: the government promised the court it would create "government agency protocols" and make sure not to abuse its power if allowed to continue searching cellphones without a warrant. "Probably a good idea," Roberts wrote after going into detail about the historical origins of the Constitutional right to privacy, "but the Founders did not fight a revolution to gain the right to government agency protocols."

In other words, self-policing doesn't cut it. The between-the-lines ace Marcy Wheeler has gone into some detail about this line, but Tim Edgar, a former official at the Director of National Intelligence, also suggested the same thing. As he wrote at the NSA-friendly Lawfare blog, "After Riley, the intelligence community has some reason to be nervous."

3. Cloud computing: 'little difference' could make a big difference

Anything the supreme court says about cloud computing has obvious implications for almost everyone on the internet, given that's where users increasingly keep their information.

At the same time, the cloud has always terrified privacy advocates because of what's known as the "third party doctrine", devised by the supreme court in the pre-digital era. The theory, as law professor Daniel Solove explained this week, "holds that if data is known to a third party, then there is no reasonable expectation of privacy in that data (and, as a result, no Fourth Amendment protection at all)."

One appeals court has knocked holes in this idea, at least when it comes to the content of your emails. (And, thankfully, all the big email providers still force the government to get a warrant to search your emails.) Still, the supreme court hasn't addressed the third party doctrine directly in decades, meaning various local and federal government agencies – not just the NSA – think that as long as a third party holds your data, it's potentially fair game.

But Roberts called into question this distinction when he wrote that it "generally makes little difference" whether data in your cellphone is stored locally or in the cloud. This may seem like a throwaway line, but it could hold significant sway down the road.

Of course, much of this amounts to reading the tea leaves, and the justices may shift course when national security or purely third-party records get involved. As the law professor and blogger Orin Kerr noted in his analysis of the Riley opinion, "I suppose there's something for everyone if you look hard enough." And we know the Justice Department, never willing to rest while privacy rues the day, will try to find every way which around the warrant requirement. It only took them a couple hours to say so.

But we know this: in the last two cases heard by the supreme court directly concerning technology and the Fourth Amendment, the government has lost to the justices by a combined score of 18-0. And with Roberts's newfound technological acumen, along with his penultimate paragraph, those of us terrified about the potential consequences of the court's lack of experience with technology can rest a little easier:

Trevor Timm (@trevortimm) Mic drop. pic.twitter.com/SiGgYJj7BF

As Wheeler noted, "get a warrant" was once just the tagline for noted hippies and privacy geeks. Now it's got a new face: the chief justice of the supreme court.