An Idaho federal magistrate judge refused to issue a search warrant forcing someone accused of having child pornography to unlock their cellphone with a fingerprint.

The ruling, which didn’t identify the accused person by name or gender, cited the U.S. Constitution’s Fifth Amendment, which says people can’t be forced to incriminate themselves, and its Fourth Amendment, which limits searches. Using a fingerprint to unlock a Google Pixel 3 XL phone seized in a search of the person’s home would effectively force them to testify about their ownership of the phone, Chief U.S. Magistrate Judge Ronald Bush wrote.

“In sum, what the Government would characterize as innocuous is instead a potentially self-incriminating testimonial communication because it involves the compelled use of biometrics — unique to the individual — to unlock the phone,” he wrote. “The Fifth Amendment does not permit such a result.”

Other judges have also denied law enforcement requests to unlock phones with fingerprints and facial scans, citing similar logic, Forbes reports.

The routine use of encryption on smartphones and the amount of personal information they often contain have led to a number of legal disputes over law enforcement searching them. Civil liberties groups are currently suing Customs and Border Protection and Immigration and Customs Enforcement over their policies on searching electronics at the border and at airports when people arrive from overseas.