| Contracting Parties | Signature | Ratification (Instrument deposited on) |
Entry into force |
| BELGIUM | 27.09.1956 | 06.02.1975 | 08.03.1975 |
| FRANCE | 27.09.1956 | 12.08.1957 | 15.03.1958 |
| LUXEMBOURG | 27.09.1956 | 20.04.1960 | 20.05.1960 |
| NETHERLANDS | 27.09.1956 | 13.02.1958 | 15.03.1958 |
| SWITZERLAND | 27.09.1956 | 13.10.1958 | 13.11.1958 |
| TURKEY | 27.09.1956 | 16.06.1958 | 16.07.1958 |
| + GERMANY | 27.09.1956 | 23.11.1961 | 23.12.1961 |
| + AUSTRIA | 27.09.1956 | 01.09.1965 | 01.10.1965 |
| + ITALY | 27.09.1956 | 07.11.1968 | 07.12.1968 |
| + PORTUGAL | 27.09.1956 | 28.01.1982 | 27.02.1982 |
| + SLOVENIA | 27.09.1956 | 01.12.1992 | 31.12.1992 |
| + CROATIA | 27.09.1956 | 22.09.1993 | 22.10.1993 |
| * NORTH MACEDONIA | 27.09.1956 | 15.04.1994 | 08.09.1991 |
| * BOSNIA-HERZEGOVINA | 27.09.1956 | 11.10.1995 | 06.03.1992 |
| * SERBIA | 27.09.1956 | 16.10.2001 | 27.04.1992 |
| * MONTENEGRO | 27.09.1956 | 26.03.2007 | 03.06.2006 |
| + accession
*succession |