TLS-1.3 mandate letter

A TLS-1.3 mandate letter is a letter that is sent to a server-owner by a domestic intelligence agency,
which orders the server-owner to make their server, and thus any websites thereon,
compatible with only TLS-1.3 encryption, and to reject unencrypted connections as well.
That serves to make incompatible the older browsers which have
a javascript-disabling option and a stylesheet-disabling option.
TLS-1.3 mandate letters typically include a gag-order,
which forbids the recipient of the letter from telling other people that they have received the letter.
TLS-1.3 mandate letters are used by the domestic intelligence agencies of various countries.
The U.S. National Security Agency (NSA) started sending TLS-1.3 mandate letters
at least as early as 2019.