Yes they can. Even if they weren't posted as 30.06, the law says you cannot take your weapon "on the premises of any government court, or offices utilized by the court". Since "premise" is defined as "building or portion of a building", the question becomes where does the "portion of the building" under the court start. Is it only on their floor, does it start at the front door to tax office. Unfortunately you do not get to provide a answer to that question, because the building is posted 30.06 anyway. I think that Potter county is doing you a favor by posting 30.06, letting you know up front. Otherwise if no sign was posted, you might carry into the building and be breaking the law and never know it.
The law does not make distinctions between a civil court, criminal court, justice of the peace, etc. A court is a court, and if there is a court in the building you are prohibited from bringing your weapon into the building.
BTW, this should have been covered in your CHL class, as PC46.03 is a pretty important piece of law to know.