I can't believe the defense wouldn't be able to present an expert witness / cross-examine the prosecution's on the distinctions between "encoding" and "encrypting."
If Wikipedia tells you how to read something, it is not encrypted.
If base64 is an encryption, then so is jpeg or *.docx .
I guess base64 is cryptographically a substitution cipher with a public pad. Which... you'd think using a ~2000+ year old method in a known-harmful way would stretch the term.