Talk:Pulsed Ray Shield/@comment-32545975-20170712143507/@comment-454133-20180207174035

Everything on your ship must be legitimate when you bring it to the table. If any of the cards are not allowed (failed requirements, slot removed by another upgrade like TIE Shuttle, etc), then you have an invalid list.

These requirements no longer apply once you're playing the match (so losing a title that provided crew slots doesn't remove the crew), but your list has to be valid when you start playing. The card's requirements keep mattering even after you've added it to the ship, so adding something else can indeed make Pulsed Ray Shield invalid.

While some video games would allow such tricks of adding and removing equipment in a particular sequence to pull off equipping an otherwise impossible item (I'm specifically thinking of certain Diablo-style games), X-Wing doesn't work that way. More specifically, if you're removing an upgrade card or pilot from your list strategically during list building, you're doing it wrong. If you're hoping a card's requirements only apply while first equipping it, listen to Akbar, IT'S A TRAP. ;)  Because requirements are continuously checked, any such finagling gets you nowhere.

I hope that explains it a bit better.

TL;DR: when you show your list to your opponent at the start of the game, they can check requirements on the spot. If anything's rules are broken, your list is invalid. Pulsed Ray Shield on a ship with 2 shields is invalid, regardless of how you got there.