Adult jardinies, I think, are out of the question. Just one. Babies/juvies - I'd not risk either. Mine two 6"-ers tried to fight even in a 6'x6'x3' pond. Other keepers say they could successfully combine small jardinies.
Bowfin? Depends on their size. They can easily eat up the aros. But the sub-adult and adult jardini aros are so aggressive, that they may kill a smallish bowfin too.
Legality in Cali I have no clue about. There is no fed ban on bowfins.