The US said that encryption (well, good encryption) was a
munition and so you needed an export license to make it available outside the US, e.g. by putting it on a web site.
Such rules are not unusual for physical objects - why sell your enemies or even potential enemies the rope they will hang you with? But for encryption it doesn't make sense because it's just information, and unlike physical objects, after writing is invented humans can trivially reproduce information, so too bad.
Eventually they whittled the "export license" step to something like a form letter Fax and IIRC Mozilla had a process where you raised a Bugzilla ticket, that caused the appropriate fax to be filled out and sent, so that was part of the release process, making it as painless as possible to comply with the stupid law.
(And now it's gone altogether)