All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is permissible to work in a non-Muslim country in any job that does not involve committing a sin or helping in it as is the case in a Muslim country. However, if the work is forbidden, or that it helps in what is forbidden, then it is not permissible to take this job; Allaah Says (what means): {Help you one another in virtue, righteousness and piety but do not help one another in sin and transgression. And fear Allaah; indeed, Allaah is severe in penalty.}[Quran 5:2]
No doubt, working in non-Islamic courts in the mentioned country involves religious prohibitions so it is not permissible for a Muslim to work in these courts. Indeed, there is in the lawful jobs what makes one in no need of the unlawful ones, and the earth of Allaah is vast, Allaah Says (what means): {It is He who made the earth tame for you, so walk among its slopes and eat of His provision and to Him is the resurrection.}[Quran 67:15]
Allaah Knows best.