My wife came back recently from a vacation to her home country. Green-card permanent resident alien. Detained at customs in the airport for three hours. She sat by herself in a room with no knowledge of why she was being detained. After three hours, an officer came into her room and said, "You're clear to go." She asked multiple times to multiple personnel why she was being detained, and everyone said, "We're not at liberty to say."
Six years ago, my sister-in-law was immigrating to the United States for the very first time. She came over on a fiance visa. Prior to her arrival, they had decided to wed in her host country before coming over to the United States. My brother called USCIS on three separate occasions to see if this would be acceptable.* Three times, the helpline said yes. When my sister-in-law arrived at her port-of-entry, the customs official casually asked where they were going to get married. My brother said that they had already wed overseas and had plans to visit the immigration office the following day to file the change-of-status paperwork. The officer immediately detained my sister-in-law, made a few calls, then provided her and my brother one last opportunity to exchange luggage, say goodbye, and then placed her on the same plane on the return flight back to her home country. There was no opportunity to argue, make phone calls to lawyers, senators...nothing. Another ten months, 32 pages of government paperwork, and $800 dollars in immigration fees later, and she finally stepped foot on American soil.
You show me a customs officer, and I'll show you a sadist. Nothing gets these people more excited than the opportunity to concurrently fight terrorism and inflict misery in the process.
* For those ignorant to the immigration process, the line between a spouse and a fiance is not as defined as you may think. In fact, most spouses immigrate to the United States on a fiance visa, because it's faster to file and process. (Google "Immigrating a spouse using a fiance visa" and find out for yourself.) But legal-story-short, the way my brother did it was not the way the customs agent accepted it, despite three different representatives at the USCIS saying otherwise.