They just haven't resulted in any rulings yet... which is why Democrats are trying to avoid them in this case. They can't wait several months for the fight to work through the courts. Instead, they're just insisting on document production with the threat that refusal to do so will be considered as obstruction and result in another potential impeachment count.
But the misunderstanding here is the difference between subpoenas related to civil/criminal court cases, and those from Congress to a co-equal branch of government. In the former, the executive branch (prosecutors) have received permission from the judicial branch to force you to show up in court (or product documents, etc.). BUT the judicial branch recognizes that you haven't had an opportunity to give your side, so you can go to the judge and ask that the subpoena be "quashed". You're basically appealing the court's decision to approve the prosecutors' request. Absent that appeal, the subpoena is presumed to be valid and you can't ignore it.
Congressional subpoenas are different. They aren't pre-vetted by a judge. Their presumed validity is further damaged when the subpoena targets the executive branch. If a conflict ensues, the most common path is for the target of the subpoena to refuse to comply - which forces Congress to take the matter to court. Such matters usually end up with a negotiated agreement between the two branches, because neither is certain who would win in court.
= new reply since forum marked as read
