Yes, JUSTICES is a Scrabble word!

Letter values in Scrabble US: J 8, U 1, S 1, T 1, I 1, C 3, E 1, S 1.

Is it a valid word?

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

the quality of being just or fair
judgment involved in the determination of rights and the assignment of rewards and punishments
a public official authorized to decide questions brought before a court of justice
the United States federal department responsible for enforcing federal laws (including the enforcement of all civil rights legislation); created in 1870

Also: department of justice, justice department.

Not playable in Scrabble US: DOJ.