I've heard it mentioned many times by colleagues and other information security professionals that it is a violation of Federal Information Processing Standards (FIPS) regulations for an internet-facing web server to accept cipher suites containing the MD5 or RC4 algorithms, during the server's SSL or TLS negotiation process.
I know that there are others which are also disallowed, but I haven't been able to find a citation anywhere in the authoritative literature that flat-out says "MD5, RC4, ... are not allowed". Note that the context of use is within a federal information system; hence, compliance with FIPS regulations is rather mandatory, and not simply advisory as it would be for a commercial organization.
In order to help my organization understand that there may be a regulatory compliance issue, I would like someone to point me to literature from NIST (or whichever other organization created/enforces FIPS) specifically blacklisting the use of MD5 and RC4 in the context of SSL connections to Federal information systems.
If it makes a difference, yes, the system may potentially need to handle personally identifiable information (PII), so any regulations contingent on that should be pointed out as well.
As some more info: I have been able to design a custom security tool that actually limits the advertised SSL cipher suites when it negotiates with the server. This allows me to test the server against a hypothetical client that does not accept more secure algorithms such as SHA1 for the message digest and RSA for the encryption. It goes without saying that, if there is a regulatory compliance issue, then it would easily override any concerns about compatibility with clients that don't support FIPS-compliant algorithms.