https://www.reuters.com/article/us-facebook-encryption-exclusive/exclusive-in-test-case-u-s-fails-to-force-facebook-to-wiretap-messenger-calls-sources-idUSKCN1M82K1

U.S. investigators failed in a recent courtroom effort to force Facebook to wiretap voice calls over its Messenger app in a closely watched test case, according to two people briefed on the sealed ruling.