Ehrentreu was a leading authority in all areas of Jewish law, with particular expertise in the fields of Medical Ethics, Conversions and Kashrut.
He has presented to the House of Lords Select Committees on medical ethical issues, such as stem cell research and euthanasia.
[4] The Chief Rabbi commented when Ehrentreu announced his retirement, "The Dayan possesses a rare combination of authority, wisdom, compassion and understanding of our community.
"[5] Dayan Ehrentreu was the rabbinical European religious authority of Tiferes Bais Yisroel, an organisation founded to reinforce halachic standards for conversion.
The eruv itself is an 11-mile enclosure in northwest London encompassing some of the city's Jewish neighbourhoods, including Golders Green and Hendon, plus much of Hampstead Garden Suburb and some of Finchley.
[11] Ehrentreu was involved in controversy in the summer of 2003 when he banned Rabbi Dr. Louis Jacobs from taking part in a synagogue service on the Sabbath before his granddaughter's wedding.
This led to heated debate in the Jewish community with some condemning the decision as petty and vindictive, whilst Ehrentreu and Rabbi Lord Jonathan Sacks argued that Jacobs could not appropriately say the blessing on being called up to read the Torah, because of his beliefs about its authorship.