Your cellphone company knows where you are at all times. Should the government know too?

That’s the question the Supreme Court will take up this week in the case of U.S. v. Carpenter. And it’s one that the “plain text of the Constitution” can’t answer.

Each year, law enforcement agencies place hundreds of thousands of requests to cellphone companies to turn over people’s “cell site location information,” including pings, which your phone emits regularly and which reveal, with a high degree of precision, where you are at any particular moment.

The government does all this without a warrant, meaning they could be surveilling everybody at all times. Pursuant to a 1986 law, law enforcement need only produce “specific and articulable facts showing that there are reasonable grounds to believe” that the requested records “are relevant and material to an ongoing criminal investigation.”

That is much less than the “probable cause to believe a crime has been committed” that’s necessary to get a warrant. And while it catches some bad guys – including Timothy Carpenter, now appealing his conviction for coordinating a series of robberies – it also represents a significant expansion of the surveillance state, worrying civil liberties advocates, journalists, and, well, anyone who doesn’t want Big Brother watching over their shoulder.

Is any of this constitutional? That’s what the justices will decide. If obtaining these records constitutes a “search and seizure” under the Fourth Amendment, then the government must obtain a warrant first. If not, then it needn’t.

The government says that since we all hand over this data to cellphone companies anyway, we have no “reasonable expectation of privacy” regarding it, in the parlance of Fourth Amendment law. It’s not secret if you’ve already turned it over to someone; it’s not even really your information anymore. This has been the court’s doctrine for forty years.

Besides, location information isn’t like a phone tap (which does require a warrant). It doesn’t reveal who you called or what you said – only where you are. According to the government, it’s a trivial invasion of privacy, more like a phonebook than a bug.

On the other hand, Carpenter and a bevy of civil liberties organizations argue, 2017 is not 1986. These days, cellphones are practically essential devices – something Chief Justice Roberts remarked in a 2014 opinion – and we don’t really have any choice but to turn over location information since it’s necessary for phones to work.

More broadly, the net effect of extending that 30-year-old doctrine would be to allow the government to track us all the time. Law enforcement could go on fishing expeditions, using location data to connect the dots. As twenty media organizations argued in an amicus brief, it would also compromise journalists working with confidential sources, since the government could pinpoint their locations. Just the fear of such intrusion might discourage sources from coming forward.

It’s easy to see both sides of the argument. On the one hand, you’ve signed over that information and it’s limited in nature. On the other hand, this is exactly the kind of “general warrant” that the Fourth Amendment was designed to prevent: allowing government to snoop on you. It’s tyranny enabled by technology.

How to decide? These days, it’s conservative orthodoxy to be an “originalist” and interpret the Constitution according to the “plain meaning of the text,” as Justice Neil Gorsuch recently crowed at a Federalist Society event, practically a victory celebration for the hard-right organization which hand-picked him.

Unfortunately, Gorsuch’s philosophy basically tells us gornicht. Nothing.

The Fourth Amendment, ratified in 1789, states that “the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Not surprisingly, nowhere in that 1789 text is the term “cellphone” recorded. Therefore, since the “plain text” of the Constitution says nothing about cellphones, the government can clearly do whatever it wants. Right?

Of course, we can look beyond the text of the Constitution: as the ACLU has noted, the first Supreme Court decision interpreting it said of a wrongfully searched man, “It is not the breaking of his doors, and the rummaging of his drawers, that constitutes the essence of the offense,” but rather “the invasion of his indefeasible right of personal security” and the state’s encroachment on the “privacies of life.”

Those broader concerns would warrant including cellphone data within the Fourth Amendment, and indeed, the Court, in an opinion by Chief Justice Roberts, held that police must get a warrant before searching a cellphone’s information.

But then, those words aren’t in the plain meaning of the text, are they?

Clearly, a more constructive approach than “originalism” is required when interpreting an 18th century text in the context of 21st century technology. The Founders could not have imagined telephones, cellphones, or GPS, so we must extrapolate from what they did comprehend to what they did not.

Unfortunately for conservatives, if we expand “houses, papers, and effects” to include electronic records on someone else’s computer, how do we not expand “marriage” to include two women or two men, or expand “due process” to include the government regulating a woman’s uterus? That’s why conservative legal fundamentalists invented “originalism” in the 1970s and 1980s.

“ The Founders could not have imagined telephones, cellphones, or GPS, so we must extrapolate from what they did comprehend to what they did not. ”

But originalism is bogus, and Carpenter shows why. The constitution is a living document, well designed for changing times. We must work by analogical reasoning to determine whether cellphone location data is more like the private papers of an eighteenth century property owner, or more like the public register in which his address was listed.

Doing so doesn’t dictate the outcome in a close case like Carpenter, but it shifts constitutional interpretation away from being a naïve enterprise in amateur intellectual history and toward a more sophisticated effort involving textual hermeneutics, scientific data, and logical reasoning.

Now words like “reasonable expectation of privacy” take on more serious meanings. As the Electronic Freedom Foundation said in its amicus brief, most Americans do not feel comfortable with the government tracking them without probable cause; to a majority of Americans, that isn’t reasonable. And that is relevant for interpreting the constitutional text.

Nor does requiring a warrant make law enforcement impossible. It just means it’s not unlimited. When the cops pursued Carpenter, they should’ve gotten a warrant for that cellphone information. It seems clear that they would’ve been able to, because they had been investigating him for a while and would’ve been able to show probable cause.

Indeed, with a less blinkered view of jurisprudence, the Supreme Court might also better understand the 1986 law at issue. Maybe allowing police to obtain phone records without a warrant was constitutional in 1986, when phone records were sparse and vague. But maybe it isn’t in 2017, when they are ubiquitous and detailed.

Times change, technologies change, and circumstances change. In Carpenter, we’ll learn whether the Supreme Court can change along with them.