For over 25 years, Jack has specialized in wealth tax matters for international private clients. He is widely published on various matters in the U.S. and abroad. He presents at international, as well as domestic conferences, on various international private client matters and investment, in the U.S. real property. He acts as outside counsel and consultant for a number of U.S. and foreign trust companies, on highly complex foreign trust matters.

In 2004, Jack had an article published in Trusts & Estates professional journal, namely, Foreign Trusts: The Capital Loss Debate. This article is still regarded, in the professional community, as the standard for U.S. tax treatment of net capital losses for U.S. beneficiaries of foreign non-grantor trusts.