Originally Posted by
LupineChemist
Just to hit this point, If you have an EU/EFTA/CH passport, you are obligated to enter the EU under that passport, just as how you are required to enter the US under your US passport.
Problem I have with your statement is I am leaving the US and on my US passport. I always return to the US on my US passport. Several years ago I tried to enter at Ireland using my EU passport but I had shown BOTH to Irish customs. I was advised to since I started with US passport to continue using this for rest of my journey.
SO I don't think "obligated" is mandatory just an option for the traveler.