Like so much on here, there is widespread ignorance of the law. For our US colleagues, easyJet is a UK-based company with bases all over Europe and employs pilots on different contracts depending on which country they are based in due to different taxation, employment laws, pensions, social security arrangements etc. They nonetheless operate to a common set of SOPs and so a Berlin-based French captain can be called out to operate in Italy etc.Love her or hate her, Margaret Thatcher basically destroyed the power of the Unions in the UK. Her legacy is is that UK laws are absolutely anti-union and there are specifically no protections in place for those who try to have sympathetic strike action, secondary picketing etc. Therefore it is common practice to use UK-based crews to cover strike action elsewhere. So if a UK-based pilot were to refuse to operate out of AMS, that would open him/her up to disciplinary action. Unless you live in the UK, you do not understand how it works, but any UK-based pilot will tell you that to refuse to go is not really a credible option.