Suggesting that Bill of Rights-architect James Madison would be "aghast" at the NSA's data collection, Leon agreed that an injunction requested by the plaintiffs should go into effect — in other words, he ordered a halt to the data collection, finding that the behavior likely intruded on the plaintiffs' constitutional rights. There are several caveats. The injunction applies only to the plaintiffs, not each of the 300-plus million Americans that use cell phones or landlines. Leon also stayed the ruling, deferring any injunction until the ruling can be appealed.

The message from the judiciary is nonetheless clear: the NSA's surveillance apparatus goes too far. And even if Leon's decision is reversed on appeal, there are a vast number of lawsuits still waiting for decisions.

(It's worth noting that the decisions made by the FISA Court, that secret "rubber-stamp" court that has in the past approved the NSA's data collection, are also generally made by one judge at a time.)

The executive branch

In August, President Obama created an independent panel to analyze the NSA's surveillance activities — a panel widely critiqued for being comprised mostly of former members of the national intelligence infrastructure. But according to multiple reports, the panel has delivered a series of actual reforms to the president — including reform of the phone metadata collection program.

One of the apparent proposals — which would still need to be put into effect by Obama — is to curtail the ongoing collection of those phone records. What the proposal looks like specifically isn't clear, but it could include requiring telecommunications vendors to maintain the records on-site, to be surveyed by the NSA as needed for terror investigations. In his widely derided interview with 60 Minutes, NSA head Keith Alexander appeared to try and counteract that suggestion, stating that having to pull data from individual phone vendors would slow the agency's investigations down. As Leon's decision points out, however, the NSA was never able to illustrate an occasion in which the metadata collection was able to stem an urgent terror situation. In other words, a delay would never have been a problem in the past.

To be fair, these recommendations are a long way from becoming real constraints on the agency. And as The New Yorker points out, Obama has in the past readily deferred to his intelligence officials on how to conduct their surveillance. In his interview with MSNBC's Chris Matthews earlier this month, though, the president said that he planned to impose "self-restraint" on the agency — which could mean precisely these sorts of tweaks.

Congress

Since the Snowden revelations began, members of Congress have been regularly offering reform legislation, much of it focused on the NSA's metadata collection. The Leon verdict may present a tipping point.

"This program... helps keep this nation safe. I'm not saying it's indispensable." - Sen Feinstein re NSA ruling, on @mitchellreports — Ari Melber (@AriMelber) December 17, 2013

Take, for example, California Sen. Dianne Feinstein. The chair of the Senate Intelligence Committee and unwavering booster of the NSA appears to be willing to reconsider that support. Earlier this month, Feinstein was widely critiqued for offering a "reform" bill that would merely have provided broader legal cover to the NSA's activities. On MSNBC's Andrea Mitchell Reports on Tuesday, Feinstein appears to have softened her tone on the data collection in the wake of Leon's decision.