A call for academics to "consider the moral and political implications" of their links with Israel will be illegal if it is adopted as policy by the University and College Union at its annual congress this week.
This is the view of two QCs who provided a legal opinion for the Stop the Boycott campaign, which is run by UCU members seeking to halt any actions by the union to cut links with Israeli universities and academics.
The QCs say the call, which was scheduled for debate after Times Higher Education went to press, would "expose Jewish members of the union to indirect discrimination" and falls foul of the union's own rules.
"In our view, the union and its officers are undertaking substantial legal risks if they resolve to pursue the motion in its current terms," say Michael Beloff QC and Pushpinder Saini QC.
Their opinion recommends that the motion be withdrawn.
"The rights to freedom of expression ... are not limitless and necessary and proportionate restrictions may be imposed to protect the rights of others than the speaker," the legal advisers said.
Following its 2007 congress, the union sought the opinion of another QC, Lord Lester of Herne Hill, on an earlier motion on Israel. This motion asked the union to circulate the text of a call for discussion on a boycott and to "encourage members to consider the moral implications of existing and proposed links with Israeli academic institutions".
The UCU refused to release Lord Lester's opinion but said that it had been advised that any call to boycott Israeli universities would "run a serious risk of infringing discrimination legislation".
The Stop the Boycott-commissioned opinion, from Blackstone Chambers, says there was "little doubt" that the 2008 motion had been drafted to circumvent the legal restrictions outlined by Lord Lester. "In our view, this attempt at circumvention fails," the opinion says.
The QCs say that because Jewish UCU members are more likely than non-Jewish members to have links with Israeli institutions the motion would put them at a particular disadvantage if passed.
Any member has the right to bring legal action against the union to prevent the debating of the motion, the lawyers warn.
Sally Hunt, the union's general secretary, said: "It is not for UCU to comment on legal advice received by other organisations, especially since we have neither seen the instructions the advice responded to, nor do we know the context or purpose for which the advice was given.
"There is no call for a boycott; the motions to congress call for a wider debate about what is happening over there and members will initiate that debate, as is their right, at congress.
"I have made it quite clear on a number of occasions that my personal view is that a boycott of all Israeli academic institutions is not the best way to promote a just peace. For the record, once again, that position has not changed," Ms Hunt said.