Yes, PREEMPTED is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, E 1, E 1, M 3, P 3, T 1, E 1, D 2.

Is it a valid word?

PREEMPTED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

acquire for oneself before others can do so
take the place of or have precedence over
gain possession of by prior right or opportunity, especially so as to obtain the right to buy (land)
make a preemptive bid in the game of bridge