CanWest Global's $1.95bn (C$2.3bn) purchase of Alliance Atlantis Communications hit a roadblock this morning. Unit holders of Movie Distribution Holding Trust filed court documents seeking a role in charting the destiny of Motion Picture Distribution (MPD), the releasing arm of AAC. MPD is an income fund: the trust controls 49% of MPD while Alliance controls the other 51%.

Announced in January, the buyout anticipated a split that would see CanWest take control of Alliance's broadcast assets while investment bank Goldman Sachs, which is providing most of the financing, would take the 51% of the distribution company as well as Alliance's stake in television property CSI .

Canadian regulation requires a film distribution company be majority controlled by Canadians; therefore Goldman Sachs must be negotiating with a third party to engineer another deal. This issue is at the heart of today's move.

In its application, the trust will ask the court not to allow the CanWest buyout to proceed without the prior consent of the trust. It will also ask that Alliance, CanWest and Goldman Sachs, provide all relevant information regarding the sale.

In a statement issued yesterday, Rubin Osten, chair of the special committee of the board of the trust said: ' We believe that our consent is required.' He added that 'despite repeated requests', the partners in the deal had not provided any information about the transaction beyond the public disclosure.

'While we do not want to frustrate Alliance Atlantis' proposed transaction, having not been provided with details as to how it might affect MPD or our interest therein, we must apply to the court to ensure that we can fulfill our duties and that our consent right will be respected.'

In a response issued earlier this morning, Alliance executive vice-president and CFO David Lazzarato said the deal does not require the trust's consent.

The move comes on the very day Alliance shareholders were expected to vote on aspects of the takeover.