I've wondered a similar thing for my country, but it was more out of curiosity, since I almost always encounter very friendly customs people (most end the encou

I've wondered a similar thing for my country, but it was more out of curiosity, since I almost always encounter very friendly customs people (most end the encounter with a "Welcome home!" if you have a Canadian passport, which I really like for some reason). So I asked a friend of mine who's a customs officer. He said that if you're a citizen, they pretty much have to let you into the country - but they don't have to make it easy. You can still be flagged for a hand-search of your baggage, interview/interrogation, and detention/seizure in the lead-up to either of the first two (even if you're a citizen, you still need to follow customs law). You can also be detained if they think the passport is fraudulent, but it's unlikely you'd be deported. Bottom line is that if you're an asshole to the customs officer, they can flag you to have your bag hand-searched, have a few fines issued against you (customs law is so complex that almost everyone violates some small portion of it), and place a note in your file that will make this always happen.