Twickenham looks certain to ignore the International Rugby Football Board's contentious six-month residential qualification for foreign players.
Tony Hallett, the Rugby Football Union secretary, said: "We believe that putting a blanket 180 days on the movement of players between European Union countries is a restraint of trade, and would be unsustainable in law. We would be challenged very quickly if we sought to implement the IB ruling."
The implication was that the ruling would apply even to movement of players among the four home unions, but, as Hallett pointed out, it is a bit late. Northampton have been fielding two Scots - Gregor Townsend and Michael Dods - and an Irishman, Jonathan Bell, none of whom have been resident for the statutory period.
If the ruling were to be applied it would have to be done retrospectively, throwing Northampton's results into doubt. "If we say it must not be applied retrospectively, then it sets a precedent," Hallett added.
A London solicitor specialising in employment law said yesterday: "Such a ruling would be impossible to enforce after the Bosman case where it was established that anyone can ply their trade under EU rules. Rugby is now a professional trade and cannot claim that it is a private club any longer and therefore not governed by the ruling."
It is the approach that Saracens' millionaire backer, Nigel Wray, was looking for yesterday. He said: "I am not a lawyer but I cannot believe it can be upheld in law once a game is professional and people earn their living by it."
Saracens have signed Australia's Michael Lynagh, who is due to arrive in May. Before that the Ireland flanker Eddie Halvey is scheduled to make his debut on 30 March.