It's an abbreviation of Erwägung. Swiss judgments contain a section referred to as Erwägungen, which basically set out the grounds for the judgment. You could also call them, more literally, "considerations".

However, I would steer clear of preamble/recital as that is only really used in English for contracts and (EU) legislation.

See an example here: http://www.bger.ch/index/juridiction/jurisdiction-inherit-te...