There may be some state legislation that covers this. I am unaware of any in Pennsylvania. The only federal law I am aware of that touches the subject is RESPA. You can find some information here on HUD's site.
For transactions covered by RESPA - those involving federally related mortgage loans - the buyer has the right to select the title insurer so long as the seller isn't paying for the insurance. At least that's my take on the subject.
In any case, if someone is telling you what company you are required to use for your own title insurance, tell then to take a hike. It's your real property. It's your risk and it's your money.