The takeover battle for ABN Amro has taken a further twist after a leading lawyer said the Dutch bank could sell its US unit without a shareholder vote.
LaSalle could hold the key to the fate of ABN Amro
The planned sale of LaSalle is seen as key to determining whether ABN is taken over by UK bank Barclays or a rival group led by Royal Bank of Scotland.
Should the Dutch Supreme Court follow the advocate general's advice, it will boost the Barclays bid, experts said.
The court, which rules next month, has followed such advice in most cases.
With or without
Its ruling, expected before 13 July, is considered crucial to the outcome of the two bids - both of which would represent Europe's largest banking deal.
Barclays 65bn euros (£43.7bn; $86bn) bid for ABN Amro envisages LaSalle's $21bn sale to Bank of America, a deal which ABN Amro management has already agreed.
The rival consortium, also including Spanish bank Santander and Belgian firm Fortis, has said its higher 71bn euros bid is conditional on it retaining ownership of LaSalle.
ABN Amro investors are unhappy with the firm's decision to sell LaSalle without the explicit approval of shareholders, arguing that it prevents ABN from considering bids other than the Barclays one which it has recommended.
In a ruling last month the Dutch Commercial Court backed their position, effectively blocking the LaSalle deal. But Bank of America appealed against the decision.
Advocate general Vino Timmerman's opinion - which he said was based on his interpretation of Dutch law - has seemingly tipped the scales in favour of ABN Amro's management and the Barclays bid.
Legal experts have suggested that the Supreme Court has followed the law professor's advice in 75-80% of cases.
The Supreme Court may rule on the issue or refer the matter back to the Commercial Court.
None of the banks involved were prepared to comment ahead of next month's ruling but City analysts said the latest development was clearly good news for Barclays.
Barclays bid has been accepted by ABN Amro managers
"Obviously it is quite a severe blow to the aspirations of Royal Bank," said Alex Potter, a banking analyst at Collins Stewart.
Royal Bank has said its current offer will become invalid should LaSalle be sold but it has not ruled out making a revised bid for ABN, including or excluding LaSalle.
"It is not a knockout blow but they need to rethink their strategy," said Vasco Moreno, an analyst at Keefe, Bruyette and Woods, of the Royal Bank of Scotland's position.
Barclays shares fell more than 1% on the news amid fears that it may be forced to raise its bid while RBS shares rose 1.4%.