RNF - Here is the stuff I found. Sorry for the length of everything. The link to the Manual is here. Please make sure your friend doesn't end up fixing some loophole before I get through it and back buddy. I'd hate to be the first guy caught! Please, don't let that happen here.
If there is a problem at primary inspection, then the inspector will type comments/information into the computer. Then the inspector will use a "red card" to identify the passenger's case and will physically escort the passenger to secondary inspection where CBP will then determine admissibility. The CBP inspector at secondary can then review the information in the computer from the primary inspector and also conduct a more thorough inspection. The "red card" cases are for "visitors." U.S. citizens and diplomats who have problems at primary inspection get a "blue card" and are escorted to secondary inspections. They get priority over the "red cards." U.S. citizens can be placed in secondary inspection if there is an outstanding warrant or if they were involved in immigrant smuggling.
Q: How does CBP analyze the data submitted by each commercial carrier to APIS
A: The APIS data is checked against the combined federal law enforcement database, known as the Interagency Border Inspection System (IBIS). IBIS includes data from the databases of CBP and twenty-one other federal agencies. Names are also checked against the FBI's National Crime Information Center wanted persons database.
Q: What Information Is in IBIS?
A: IBIS keeps track of information on suspect individuals, businesses, vehicles, aircraft, and vessels. IBIS terminals can also be used to access NCIC records on wanted persons, stolen vehicles, vessels or firearms, license information, criminal histories, and previous Federal inspections. The information is used to assist law enforcement and regulatory personnel.
Before any passport is issued, the passport applicant’s name is checked against a central name check system. A federal or state law enforcement investigative agency may request that a subject be placed in the passport name check system for notification before issuance even when there is no warrant or other court order. The written request should be sent to the Office of Legal Affairs (address below), and should include full biodata of the subject, the statute under which the subject is being investigated, and the agency address and phone number of the officer to be contacted.
A federal or state law enforcement agency may request the denial of a passport on several regulatory grounds under 22 CFR 51.70 and 51.72. The principal law enforcement reasons for passport denial are a federal warrant of arrest, a federal or state criminal court order, a condition of parole or probation forbidding departure from the United States (or the jurisdiction of the court), or a request for extradition. The HHS child support database and the Marshals Service WIN database are checked automatically for entitlement to a passport. Denial or revocation of a passport does not prevent the use of outstanding valid passports.
http://www.ilrc.org/resources/CBP_IFM_Feb12008.pdf is the Field Inspector Manual
12.1 Inspection of U.S. Citizens.
When you are convinced that an applicant for admission is a citizen of the United States, the examination is terminated. This is not to say that your role as an inspector is always completed at that time. Listing of the subject in a lookout system may dictate further action, such as notifying Customs or another agency of the person’s entry.
It must be emphasized that the grounds of inadmissibility contained in 212(a) of the INA are applicable only to aliens. Consequently, the examination of a person claiming to be a United States citizen is limited to matters required to establish present citizenship. Once you are satisfied the person being examined is a U.S. citizen and any required lookout query has been completed, the examination is over.
Temporary detention of a U.S. citizen for extensive questioning generally requires reasonable suspicion that the person is involved in illegal activity. Inspectors cross-designated to perform Customs inspections may, of course, continue questioning for Customs purposes. If probable cause to arrest the U.S. citizen cannot be developed within a reasonable period, the person must be released.
It is important to note that although the United States does not formally recognize “dual nationality”; many other countries do. It is not unusual to encounter a United States citizen (even native born) bearing evidence of both United States citizenship and foreign nationality. For example, a child born in the United States to a foreign national may, under the laws of that country, be entitled to its parent’s citizenship and be included in the parent’s passport. Under certain circumstances, that document may be used for identification and entry, if presented in conjunction with a birth certificate or other evidence of U.S. citizenship. Specific provisions relating to passport requirements for United States citizens are outlined in 22 CFR 53.1 and 2.
12.2 Evidence of Citizenship.
Any time documentary evidence of citizenship is required (e.g. when a passport is required of a U.S. citizen returning from outside of the Western Hemisphere) or whenever documentation is voluntarily
18 CBP Inspector’s Field Manual
Presented by an applicant, you should make an effort to review the documents. If there is any question as to the subject’s citizenship, close scrutiny is necessary to determine that the documents are unaltered, genuine, valid, and belong to the bearer. In the instance where documentation is volunteered by an applicant, you should make a cursory review of the document(s), even if your preliminary inquiries have allowed you to make a determination of the applicant’s United States citizenship. A brief review should be made, if for no other reason, because the applicant may have gone to considerable effort to obtain a particular document and may feel the Service is failing in its responsibility if the document is considered unimportant.