US firm Mayer Brown & Platt is shutting down its Brussels office as of 1 December.
Its resident partner Alan Hamburger has moved to the Brussels office of Morgan Lewis & Bockius while associate Stephen Brummel has gone to Weil Gotshal & Manges in the city. A third lawyer, Susan Launi, has been transferred to Mayer Brown's London office.
Jeff Gordon, the firm's London-based partner in charge of international practice, said: "In Brussels, you really want to have an established regulatory practice. However, we started out as a finance practice and our core partner was a tax lawyer. We didn't have the regulatory configuration you need".
Gordon added that the firm was not withdrawing definitively from the Belgian capital, but was "taking a breath to reconsider its options". The firm, he said, could establish another presence in one or two years either by allying with a local firm or setting up again with the right sort of practice.
The move underlines the difficulties some firms have experienced with their Brussels operations although others have preferred not to shut down completely.
Chris Schulten, chief executive of Richards Butler, said that his firm was "on the verge" of upgrading its office and that an announcement would be made in the next few weeks.
Although he would not be pressed on details, he suggested that the next move could involve a non-UK firm.
Richards Butler has not had any lawyers permanently based in Brussels since Katharine Baragona left the firm at the end of last year. She was promoted as resident partner the previous April.
Since then, according to Schulten, the firm has been reviewing its options which include recruiting new talent, linking with another firm or sending over more lawyers from London.