Mohammed Bouyeri, 27, is serving life for murdering Van Gogh – a strong critic of radical Islam – last year.
Bouyeri can now be tried for belonging to a “terrorist” group – his lawyers say it would be a pointless show trial.
The court ruled that even if no extra sentence could be handed down to Bouyeri, the trial would demonstrate “an adequate response from the government to criminal acts” and “public disapproval”.
Shock for Netherlands
Bouyeri told his murder trial he had acted out of religious conviction.
He shot and stabbed Van Gogh in broad daylight as the film-maker was cycling through Amsterdam.
The trial of the Hofstad suspects, arrested after Van Gogh’s death, is not expected to start until the end of the year.
Meanwhile, Dutch Immigration Minister Rita Verdonk has proposed a ban on the wearing of Muslim burkas – full-length veils covering the face – in certain public places, to prevent people avoiding identification.
Alarm about Islamist terror has increased in the Netherlands since the Van Gogh murder.
A Dutch MP who campaigned with him against radical Islam, Ayaan Hirsi Ali, defended Mrs Verdonk’s plans in a BBC interview.
She told the World Today programme that CCTV cameras, used to help track down terrorists, must continue to reveal suspects’ faces.
The CCTV operators “need to see their faces and if you cover your face you cannot be identified”.
She said the wearing of masks in the Netherlands was also prohibited except during festivals and under some special circumstances.
She said Muslim women were not obliged to wear the burka, and denied that some burka wearers would be confined to the home.
“We have to find a balance between civil liberties and security – and that debate is raging on in the Netherlands,” she said.
Last year several Belgian towns, including Antwerp and Ghent, banned the wearing of the burka in public.
Utrecht benefit cuts
The authorities in the Dutch city of Utrecht have reduced unemployment benefit for women who say their refusal to remove their burkas is preventing them getting jobs.
The measure was prompted by the case of two burka-clad women who said they did not attend job interviews.
Utrecht city council spokeswoman Sylvia Borgman said the 600-euro ( £400) per month benefit was initially being cut by 10% in such cases. Further cuts would come if unemployed women continued to wear burkas.
“For the city council it is more important to keep public support for the social services system – that overrules freedom of religion,” she told the BBC News website.
She said only a few women were affected by the measure. Utrecht is the first Dutch city to take such action, she added.
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