UPDATE 1-ASMI foundation to have no vote on shares-court

* No say in potential cancellation of preference shares

* Parties told to resolve CEO dispute by June 5

* ASMI shares down slightly

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AMSTERDAM, May 13 (Reuters) - A management-allied ASM International (ASMI.AS) shareholder body will not have a say in the potential cancellation of preferred shares it holds, a Dutch court ruled Wednesday.

The midcap company, which makes equipment used for the processing, assembly and packaging of semiconductors, has been in a drawn-out dispute with some of its main shareholders for years, triggered by underperformance at its packaging and assembly business.

In January, the ASMI shareholder foundation - an entity common with Dutch companies that is usually friendly to management - agreed to cancel preference shares issued to it. They were aimed at blocking activist investors' efforts to have the chief executive fired.

Since then, however, activist shareholders Hermes and Fursa moved to gain a better grip on company management by requesting the appointment of a special supervisory director.

The dispute between ASMI and the shareholders went back to court, mainly over the ability to appoint and sack board and executives.

In a decision issued ahead of AMSI's annual shareholders meeting on Thursday, Judge Huub Willems of the Dutch enterprise court in Amsterdam said the foundation could not participate in any vote involving preference shares.

Willems also told the parties to come to an agreement over the dismissal of CEO Chuck del Prado by June 5.

Hermes and Fursa have been trying to sack Del Prado, but the company has stood behind him and said earlier last month it would not reappoint Chief Financial Officer Naud van der Ven after he, too, urged the supervisory board to sack the CEO.

ASMI shares were down 0.3 percent at 9.72 euros in Amsterdam as of 0920 GMT. The broader mid-cap index .AMX was up 0.35 percent. (Reporting by Eva Hagendoorn; writing by Reed Stevenson; editing by Simon Jessop)