I'm sorry, WHAT?
Pirate raiders can't go through an anti-bombardment shield?
Yeah, since when?
This has been true in every version that I've tested it in, including 1.9.10. You can give the orders, and the ships will fly over the target planet, but they will not launch pods, no troops will appear on the planet's surface, and you will not receive any raiding trophies (money, technological progress, resources), nor will the target world gain the 'recently raided' message.
I test it by starting a game as a pirate faction and using the editor to spawn shields on independent (and imperial) colonies, giving myself a bunch of ships, and issuing raid orders, and it certainly appears to work for my imperial colonies when I actually build them while playing as a normal empire rather than cheating them in as target dummies in a test game as pirates. They prevent raids on the planet (after the shield completes) even if I don't invest other military assets, even when it's in an area that I have not yet secured and still see frequent pirate activity hitting ships and stations over the shielded planet, including once on a conquered independent colony in a system with a pirate space port. Cheapest way I know of for dealing with raids, as a PSG costs only about as much as two to four infantry units (depending on species) to maintain and the 20K purchase cost is basically negligible. Put five or ten infantry divisions on the planet while it builds to train them up and temporarily secure the planet, and then move them elsewhere.
My assumption is that the reason this works has something to do with the requirement that boarding pods have which prevents them from being used against shields with more than X strength (where X is I think 20 shield points to 100 shield points depending on boarding pod technology). How strong planetary shields are is not something revealed by the game, but the strength is likely significant since planetary shields block any and all bombardment weapons, regardless of how advanced they are, short of the one which actually blows the planet away; presumably this is sufficiently strong to block boarding pods designed to penetrate the weaker shields of ships which have been worn down by combat, whereas troop ships use something (be it a shuttle or the entire ship) which was designed to bypass that kind of shielding but which is sufficiently large to significantly reduce its utility for use against ships (probably, the boarding pods use a scaled-down, weaker version of this system rather than the troopships use a scaled-up, more powerful version, as any troopship can deliver troops to any planet regardless of the defenses, if the issue isn't simply that the planetary shields simply cannot stop objects the size of full-scale shielded warships from entering the atmosphere and landing troops, though then it becomes a question of how to justify the inability of a raiding warship to enter the atmosphere and penetrate the shield before launching boarding pods).
< Message edited by Aeson -- 12/14/2014 5:11:20 AM >