There was a warrant in this case. That type of warrant is now deficient and electronic data holders like Google with easily refute future attempts to get data with a clearly deficient warrant. Parallel construction typically means a warrant was not given on the first pass.

No legal precedent can prevent parallel construction, because when it is done right, nobody but the police are actually aware that it took place.

This precedent doesn't prevent parallel construction at all. In fact, it encourages parallel construction.

In this case it’s pretty simple: they won’t be able to obtain geofence warrants in the future.

Parallel construction is this huge phantom menace on the internet but something that in real life occurs less frequently than a person being struck by lightning.

Law enforcement faces a very high burden to show that parallel construction would apply. (Not "could." Would.) This generally requires law enforcement to show that they were pursuing multiple parallel paths of investigation, and that basic investigatory work in one of the other paths of investigation would have legally led to the excluded evidence as a matter of course. To put it perspective how difficult this is, a former co-worker that is still with the public defender has seen the prosecutor succeed exactly once in 15 years in making a parallel construction argument.

The DEA is the only agency that successfully makes parallel construction arguments on a regular basis, and this is primarily because the DEA has the resources to actively pursue multiple parallel paths of investigation, and because in many cases the reason for using parallel construction is that key witnesses have a tendency to get murdered....

Well they need the warrant to get Google to give them the information in the first place, so they would not have the data to create the parallel construction.

I'm confused how parallel construction plays in here, nonsense adds another layer of confusion, but an attempt to help, tl;dr: the 5th Circuit has held that requesting a list of people/IPs/devices in a location is not permissible.

I'm just trying to guess a gap: engineers tend to see law as more iron, like code, and judge law based on inverse programming: if you can find some set of circumstances that creates a gap where the law isn't obeyed.

Ex. here, you might mean that this doesn't technically stop police from requesting geofenced data anyway, using it to get suspects, then not mentioning it at trial. Yes, technically, the police could ignore this, and request a warrant, then the judge could ignore it, then the tech companies could ignore it, the DA could collude with the police to hide that happened, and pretend they found the suspect a different way.

But it's impractical.

It's hard to spell out why, exactly, tl;dr: death penalty for your career if any of this is discovered by anyone, you can't do it by yourself, and these people are generally on the same team in our distanced analysis, people are tribal, and gov't attorneys/tech companies/judges/police can't rely on eachother's silence.