AMSTERDAM (Bloomberg) — A Dutch court blocked ABN Amro Holding NV’s $21 billion sale of LaSalle Bank to Bank of America Corp. because management failed to get shareholder approval for the deal.“ABN Amro management has misjudged its task,” said Judge Huub Willems of the Amsterdam district court’s Enterprise Chamber in the ruling today, backing a complaint by the Dutch investor group VEB.

The decision may disrupt Barclays Plc’s $90 billion takeover of ABN Amro and open the way for a group led by Royal Bank of Scotland Group Plc to make a higher bid for the Amsterdam-based company. The VEB shareholder group argued to the court that the sale of Chicago-based LaSalle to Bank of America was aimed at preventing a possible bid from the Royal Bank group for ABN Amro.

“Now that the sale of LaSalle has been deemed illegal, it is much more likely that Royal Bank will win the day,” said Colin Morton, a Leeds-based fund manager at Rensburg Sheppards who helps manage $1.8 billion and owns Barclays and Royal Bank stock. “If it had been legally sewn up it would have been very difficult for the Royal Bank group,” Morton said.

ABN Amro shares rose 68 cents, or 1.9 percent, to 36.60 euros in Amsterdam on optimism a higher bid will follow the ruling. Barclays shares jumped 3 percent to 744.5 pence, while Royal bank slipped 0.7 percent on 1,963 pence ($39) in London.

Edinburgh-based Royal Bank, Santander Central Hispano SA and Fortis, the group considering a joint bid for ABN Amro, said in a statement after the ruling that they would “await ABN Amro’s response to the court decision.”

“We expect an offer by the consortium tomorrow,” said Jean- Pierre Lambert, a London-based analyst at Keefe, Bruyette & Woods Ltd. who has “market perform” rating on ABN Amro.

Barclays declined to comment, said spokesman Alistair Smith. Bank of America spokesman Scott Silvestri said the company was “reviewing the judge’s decision in the case” and had no immediate comment.

The Children’s Investment Fund, a London-based hedge fund that encouraged ABN Amro to consider a break up of the company in February, said in a statement that the Dutch court’s decision was “an essential step in rectifying a flawed sales process.”

ABN Amro Chief Executive Officer Rijkman Groenink announced on April 23 that the largest Dutch bank would be bought by Britain’s Barclays Plc, and at the same time said LaSalle would be sold to Charlotte, North Carolina-based Bank of America.

Two days later the Royal Bank-led group indicated they would pay 72.2 billion euros ($98 billion) in cash and stock for ABN Amro. Their proposal is dependent on a reversal of the LaSalle sale.