Judge Vincent Gaughan said there was no "overarching interest" in banning the videotape - which shows the singer allegedly having sex with an underage girl - from being shown to the media and public in his child pornography court case.
He said: "This is the whole crux and linchpin of the case. If there was no tape, we wouldn't have a case."
The "I Believe I Can Fly" singer has pleaded not guilty to 14 counts of child pornography.
Prosecutors claim the videotape was made sometime between January 1998 and October 2000 - so the alleged victim may have been only 13 when the incident took place.
Both the prosecution and defence had asked the judge to allow the tape to only be seen by jurors, attorneys and the judge himself to avoid further shame to the girl who is now 21.
The Cook State Attorney has said the girl will not be called as a witness in the trial.
A trial date for the case, which will be heard in Chicago, has not yet been set.