The mission statement of LFI is nothing to do with upholding British law. Or the law of England and Wales which I suspect is what you mean. On their website they say their aim is:
to provide, assist in providing, procure or promote the provision of legal support including advocacy, research, advice and campaigning in combating attempts to undermine, attack and/or delegitimise Israel, Israeli organisations, Israelis and / or supporters of Israel.
They’ve written legal opinions for example relating to Israel’s adherence to international law in the matter of the ICC arrest warrants which are totally counter to the views of other very highly regarded British Jewish lawyers for example the AG Richard Hermer. Who presumably also are very well versed in English law yet disagree with them.