| Clue | Source | Date |
|---|---|---|
| ON | Universal | 08 Dec 2022 |
| Feature of the European Union | Thomas Joseph | 12 Nov 2019 |
| Policy allowing unrestricted travel | USA Today | 18 Dec 2018 |
| Policy allowing unrestricted travel | ||
| Feature of the European Union | New York Times | 27 Jan 2017 |
| Feature of the European Union | ||
| Unprotected boundaries |