This may clear up the question.

Article 19
Support Activities Services
.....
5. The mail sent through the military post service shall be certified by United States Forces authorities and shall be exempt from inspection, search, and seizure by Iraqi authorities, except for non-official mail that may be subject to electronic observation. Questions arising in the course of implementation of this paragraph shall be addressed by the concerned Joint Sub-Committee and resolved by mutual agreement. The concerned Joint Sub-Committee shall periodically inspect the mechanisms by which the United States Forces authorities certify military mail.
There are sweeping provisions covering "import-export" packages sent outside of the MPS - some applicable to personal items.

Article 15
Import and Export
....
2. Members of the United States Forces and of the civilian component may import into Iraq, re-export, and use personal effect materials and equipment for consumption or personal use. The import into, re-export from, transfer from, and use of such imported items in Iraq shall not be subjected to licenses, other restrictions, taxes, custom duties, or any other charges imposed in Iraq, as defined in Article 2, paragraph 10. The imported quantities shall be reasonable and proportionate to personal use. United States Forces authorities will take measures to ensure that no items or material of cultural or historic significance to Iraq are being exported.

3. Any inspections of materials pursuant to paragraph 2 by Iraqi authorities must be done urgently in an agreed upon place and according to procedures established by the Joint Committee.
So, the precise scope of inspections is left to future regulations to be agreed.