Dual citizen & traveling out of a Schengen area country with a foreign passport

Question

This is a purely hypothetical question, but this scenario almost happened to me.

With dual citizenship of Poland and the US, both countries require their respective passports to leave the country. Even though I have my US passport, I apparently cannot fly to the US without my Polish passport in hand.^* However, while flying from another country (e.g. Germany) only the destination passport is required.

1. Would it be possible and legal to cross the Schengen Area border via land from Poland to another country, and then fly to the US with only my US passport?
2. If this is the case, why would such a rule be in place if it can be so easily circumvented?

^*Allegedly this isn't always enforced, but allegedly this is the law.

Answer 1

Why would you want to travel without both of your passports? This leaves you in a vulnerable position if an emergency arises where you need to travel somewhere using the other passport.

As to why the rule would be in place when it is easily circumvented, well, ease of circumvention isn't usually the prime consideration in imposing rules. The likely explanation in this case is that the rule is older than Poland's membership in the Schengen area.

However, while flying from another country (e.g. Germany) only the destination passport is required.

Would it be possible and legal to cross the Schengen Area border via land from Poland to another country, and then fly to the US with only my US passport?

Consider what would happen if you tried to leave the Schengen area with your US passport: the border officer would have to determine whether you had overstayed in the Schengen area. You would have no entry stamp and no residence permit. Of course you would not have overstayed, but the document you would use to prove that is a Polish passport (or a Polish national ID card, which is essentially equivalent to a passport in EU law).

Even if it is legal, it would be inconvenient, possibly very much so.

Answer 2

There are a bunch of partially overlapping rules that governs this

1. You SHOULD always enter and leave a country on the same passport. While this may not be strictly required everywhere. Many countries match exit records/stamps to entry records/stamps and it's an administrative nightmare if these are using different passports. In your case, country means "Schengen".
2. For countries of your citizenship you SHOULD use your native passport. For some countries like the US and Poland, that's a hard requirement. Germany, for example, is more relaxed about it. Even if you don't have to: it's good practice and as an added benefit you get to use "citizens line" at immigration.
3. You can switch passports between countries as much as you like.

Because rule #2 is a hard requirement for both of your passport countries, you are required to travel with two passports. As usual with this type of thing, there are potential loopholes or workarounds but I highly recommend against trying this unless you have a very, very good reason.

So, yes, you could potentially try to exit from Germany on your US passport, but since that passport has no entry record, they may start asking about this: Long extended discussions in an immigration back room while you are missing your flight are NOT fun.

Answer 3

1. No, just travelling through Germany on your US passport would not be totally legal and possible, unless you have a Schengen residency permit in your passport or you have stayed in Europe for less than 90 days. In Germany, your papers will be checked by border police in the airport and this will lead to awkward questions, as pointed out by phoog.

2. That said, I do not really understand the problem here. You could just take both of your passports, show the Polish passport to Polish border police and the US passport to US border police. For check-in and bording any of the two passports should be OK, though passport of your respective destination is probably more practical. In fact, instead of a Polish passport a Polish ID card should be sufficient for Polish border police, though probably insufficient for boarding the plane to the US.