Switzerland has a big complex web of treaties and agreements with the EU that make it almost, but not quite, a member. Neither the EU nor Switzerland are entirely happy with the situation; the EU doesn't like all the tradeoffs that need to be balanced just for Switzerland rather than in the standard EU bundle, while Switzerland doesn't like things like freedom of moment being made a condition of market access.

See e.g. https://www.theguardian.com/world/2016/sep/22/switzerland-vo...

More than 120 treaties as of that writing, with guillotine clause - break one, break them all.