Yes, LITIGIOUS is a Scrabble word!

Letter values in Scrabble US: L 1, I 1, T 1, I 1, G 2, I 1, O 1, U 1, S 1.

Is it a valid word?

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

of or relating to litigation
inclined or showing an inclination to dispute or disagree, even to engage in law suits

Not playable in Scrabble US: DISPUTATIVE.