Oh... I think the rule is being enforced. If I wanted to port my barrels buy say... Angle port I would simply call up Perazzi USA and have them have Angle Port do the work. The rule says the ports must be done by the "Original Manufacturer" If Perazzi does it for you its legal. There was talk that barrels would have to be reproofed again after the work but thankfully that was rejected. The question about ported chokes is less clear. They are illegal in the UK as I understand but I have seen no other places where they have been rejected. I will be interesting to see how that are viewed in the run up to the London 2012 Olympics.
The Jury must implement a program for inspecting guns and clothing.
The Jury has the right to examine any item of the shooter's equipment including clothing.
The addition of compensators and similar such devices fitted to gun barrels is permitted for skeet but prohibitted in Trap, Double Trap and Automatic Trap shooting.
Ported barrels are acceptable provided the shooter has them inspected by the Jury prior to the start of the competition and they are found to meet ISSF requirements.
Dispersion Effect Changes
No internal changes may be made which will give an extra or special dispersion effect, such as the inverse loading of components, crossing devices, etc.
Translation. Compensated chokes are are permitted in skeet only. Difussion chokes are not permitted in any event. Ported barrels are permitted provided the Jury has inspected them and approves.
The stickers that you see on the firearms in the pictures are from the Jury and placed on the gun after inspection. Each gun has a sticker placed on it prior to the competion by the Jury, and yes the do check them.