It could be illegal for them to use that. Perhaps the party does the redistricting which an assembly member introduces into the legislature. To use the database, it would either need to be publicly available or else the executive would have to do the gerrymander. (Which might be how it works. But I live in a place where good government is valued.)
Why on Earth does the legality matter? It's not like they'd ever admit they are gerrymandering. What data they use to optimize their gerrymander is irrelevant.
