Both of them are US export control regulation, but they are different. Focusing the difference between ITAR and EAR, here's some tips for understanding ITAR.
- U.S. State Department's Directorate of Defense Trade Controls (DDTC) administers International Traffic in Arms Regulations (ITAR). On the other hand, U.S. Department of Commerce's Bureau of Industry and Security (BIS) administers Export Administration Regulation (EAR).
- ITAR govern export of Defense articles and services. EAR control most of other dual-use items.
- Defense Articles are listed on ITAR's United States Munitions List (USML). USML is divided into 21 categories numbered I to XXI. Dual-use items subject to EAR is listed in EAR's Commerce Control List (CCL). CCL divided into 10 categories numbered 0 to 9. CCL further divided into 5-digit ECCN, e.g. 9A991.
- ITAR trumps EAR. Item subject to ITAR is not subject to EAR. (Even if ECCN specifically describes item, or even if BIS has classified item in a specific ECCN in writing ruling)
- What is ITAR controlled? Broadly speaking, was the item (regardless of how it is used now) originally specifically designed, developed, configured, adapted, or modified? For a military application, military end-item or a commercial satellite, spacecraft, or launch end-item or application?
Precise jurisdictional determinations are the most fundamental and most important part of any export compliance program. If item is subject to the jurisdiction to the ITAR, then there are almost always significant licensing requirements!