Originally Posted by
cestmoi123
There is, however, a substantive difference between requiring an exit visa and refusing to issue someone a passport. They are, in many cases, de facto the same, of course, but refusing to issue a passport just means that a country won't help that citizen gain admission to another country.
As far as I know, there's no legal requirement that a US citizen have a passport to board a flight to another country - the carrier won't generally transport the passenger, but that's because of concerns that he/she won't be admitted (and the carrier will face fines from the destination country).
The US has de jure and de facto demanded that common carrier airlines require passenger passports, NEXUS card, or passport replacing docs as a condition to transport recognized US citizens (and others) out of the US. This was done by the US under a US move referred to as the WHTI. If US carriers ignore WHTI when flying passengers out of the US, the carriers are subject to a penalty.
In other words, these restrictions are not merely a product of destination country rules, and this is something that is still evident with regard to air travel by US citizens who arrive in Canada and use a US state driving license and US state birth certificate to seek admission into Canada at a Canadian airport of entry.