One of the problems that we can run into with ITAR is the "exporting" of technical data that happens when posting information related to the manufacturing of arms defined in the following link.
International Traffic In Arms Regulations - PART 121-THE UNITED STATES MUNITIONS LIST
If any of you are familiar with the legal hassles that Defense Distributed is having with the Ghost Gunner and the distribution of CNC files for that machine, then you know how ITAR can effect the posting of "how to" information related to our hobby.
You can post onto a forum "I drilled a hole to allow...." and that's OK because no one can use that information to construct a device defined in Part 121 of ITAR. You haven't made enough technical information available with that kind of statement.
But if you post "I drilled a 0.125" dia hole that was 0.500" directly above datum X to allow...". You may have just "exported" technical data that would allow someone in an export controlled country to construct a controlled munition.
Distribution of a CNC program that machines an AR15 lower is, unfortunately, tecnhical data that is controlled by ITAR and posting it onto an internet forum is exporting. To do so requires an export license with state department approval. They don't give blanket approvals either. You must know who will receive the technical data and that the data will not be re-exported without an additional state department license and approval.
If you're in the business of making firearms, you are already restricted from exporting firearm parts to outside the US w/o the proper export licensing and approval.
ITAR expands the export restrictions to include technical data.
Exporting technical data can happen by sending blueprints, posting onto the internet, and even talking over the phone.