If they don't have the private keys and use them to move the balance to addresses that only they control, they didn't really seize anything.
Bitcoin seems so terrible privacy wise. It's so much more traceable than cash. I don't know why people don't just use monero. That'd be like everyone on the planet drives the same car, and the only way to identify yours would be to have the keys to it. The analogy works because monero takes a long time to identify yours with your key - you have to check every "car". That's one of the major technological downsides to it unfortunately.
"condiders", insofar as governments are concerned only reaches as far as their sovereignty does. In the case of Ireland, that IIRC, 12 miles from their shores [1]