Police this past week seized a server at Amsterdam Science Park in Oost at the request of the United States.
It belonged to Autistici/Inventati (A/I), an Italian anti-capitalist and anti-fascist internet provider.
The industry association Dutch Cloud Community (DCC) has sent an urgent letter to the police asking for the legal basis of the seizure.
Cloud sector fears a loss of trust
DCC says it is unclear whether any independent Dutch legal review took place, and warns that without one the Netherlands will lose the trust of companies storing data here.
It accepts that international cooperation helps fight crime, but says it must not be used to suppress political expression.
Prosecutors say data not yet shared
Amsterdam prosecutors say they acted under the Dutch-US treaty on mutual legal assistance in criminal matters and had no grounds to refuse.
The seized data has not yet been shared with the US.
Provider dissolved itself after sanctions
For about 25 years, A/I offered free email and web hosting to around 20,000 activists and civil rights organisations worldwide.
The US calls it a terrorist organisation serving far-left groups, and after US sanctions in late August, A/I dissolved itself as a precaution.