"INS" is the American department of immigration (not sure what exactly "INS" stands for, except if you say "INS" to a newcomer to the US, they go pale). One can have work visas or student visas to the US or Canada, but she's been with him for over two years now, and I do think it's passing strange that she's the one he takes out in public, not the mother of his youngest child who is still listed as his official "companion".
I should stop this, actually; it's just that this is a puzzle and I have to solve puzzles - it's a compulsion, or something!
By the way, I'm not saying he married her is a statement of fact; just that it's one possibility. Immigration laws are very strict in the US, especially after 9/11, and there are very few legal ways she could stay with him in the US without the immigration department kicking her out.
It'll be interesting to see what the Biography will show, since that will be more up to date than the E! True Hollywood Story, which stopped at 2002.
Interesting to note that the last time a photograph of Steven and Arissa in public was taken was December 8, 2002 (although she was with him on CNN in August 2003 after the Gotti verdict came down).