The phrase "all but prohibited" is correct and usable in written English.
It is typically used to indicate that something is almost completely forbidden, but not entirely so.
Example: "The new regulations make smoking in public places all but prohibited, with only a few designated areas allowed."
Alternatives: "virtually banned" or "effectively outlawed".
The Catholic hierarchy here, which has all but prohibited public discussion of real-life misdeeds by the church, responded by mounting nationwide protests to stop the movie.
Dr. Yalow told interviewers that she had known from the time she was 8 years old that she wanted to be a scientist in an era when women were all but prohibited from science careers.
Thanks to the efforts of people like Norberg-Hodge, you are faced with signs flying from the lampposts of Leh saying "Say No to Polythene," and plastic bags are all but prohibited in town.
At LAX, it still appears as if public transportation is all but prohibited.
The death toll on both sides is nearly impossible to verify, since journalism is all but prohibited in the region, but the Egyptian government claims militants have killed hundreds of police officers and military personnel.
Its Constitution all but prohibits foreign control of energy production.
Audrey plies Alike with frilly, feminine clothing, and she all but prohibits the casually butch Laura from visiting.
Indonesia's rules for foreign doctors all but prohibit hospitals from recruiting them.Second, regulations can be treacherous.
The basic blueprint was established by elite institutions more than a century ago, and according to critics, it all but prohibits the law-school equivalent of the Honda Civic — a low-cost model that delivers.
The high cost of producing a contemporary Olympics all but prohibits developing countries from bidding and staging the Games, Romney said, and he and many other Olympic officials are in favor of making the event smaller.
Germany's employment laws, for example, all but prohibit contract labor.
