No concrete reason for the TrueCrypt shutdown has emerged, giving way instead to speculation that perhaps the developers abrupt decision is a warrant canary. Apple s first transparency report, released last November, contained two sentences that made it stand out from the rest: Apple has never received an order under Section 215 of the USA Patriot Act. We would expect to challenge such an order if served on us . Many interpreted that declaration as a signal that Apple had yet to receive a secret court order or National Security Letter.
Source: https://threatpost.com/of-truecrypt-and-warrant-canaries/106355/