A Texas appeals court has struck down a law allowing police officers to conduct warrantless blood tests on suspected drunk drivers.

The law borrows concepts from the Texas Transportation Code and other statutes, and has both attorneys and Fourth Amendment advocates up in arms over what it means to conduct an “unreasonable search and seizure.” In 2013, the Supreme Court ruled in Missouri v. McNeely that the natural dissipation of alcohol in the bloodstream does not constitute an exigent circumstance justifying blanket authorization for warrantless searches. Texas’ “No Refusal” periods, however, throw a wrench in an easy hypo by injecting statutorily-based “implied consent” into the mix. (“No Refusal” periods are exactly what they sound like.)

What happens if you refuse to provide a sample and/or perform sobriety tests in the field? Up until last week, the authorities would haul you into jail and forcibly extract the evidence from the crook of your right arm—without a warrant. The convenience of this level of “implied consent” was too much for the Texas Criminal Court of Appeals, however, and last week they ruled this type of search unconstitutional.

Via the Houston Chronicle:

“We hold that a nonconsensual search of a DWI suspect’s blood conducted pursuant to the mandatory-blood-draw and implied-consent provisions in the Transportation Code, when undertaken in the absence of a warrant or any applicable exception to the warrant requirement, violates the Fourth Amendment,” Judge Elsa Alcala of the Texas Court of Criminal Appeals wrote on behalf of the five majority opinion judges. Four members of the nine-judge court dissented.

Constitution trumps statute, and it feels so right.

Accusations that when used, the warrant process for these types of convictions is little more than a rubber stamp aside, this is a great development for the Fourth Amendment. The ruling won’t kill No Refusal as a whole, but it will limit the admissibility of evidence obtained without a warrant.

Courts should be careful with their assessments of exigency; normally, evaluation of exigent circumstances happens on a case-by-case basis—the window in the convict’s apartment breaks, the woman screams, the gun fires—which makes sense considering the standard lives or dies at the hands of circumstance. To grant a blanket stamp of exigency onto the changing chemical makeup of a suspect’s blood wouldn’t just set us teetering at the top of the slippery slope; it would send us careening down headfirst with our pants down.