Policing the cheaters

According to chess.com - completely legal - since you found it in an on-line database. In my humble opinion, you're not playing if you're doing that, though. You're copying Kasparov (or Karpov, or Fischer, or whoever).
You are wrong - it is a part of chess. There are >1000 GMs in the word today, and hundreds of top-players through history - yuo need not to investigate all from the first move!
Every master in OTB, CC or on-line chess do it - copying great examples. Fresh ideas in opening are rare. A difference is that in OTB game you need to have all it in your head - so you need to have an excelent memory to be a master. In our way of play, you can use "external memory" (databases and books); however, CPU need to be your own!
And in every game you wil come "out of books" at some points, usually between 10th and 15th move. If you, in the first phase of the game, only coppy moves, you dont understand ideas and probably you will lose in midlegame agaist an experienced oponent. You need to study openings all the time, and search for new ideas.
I published here some of my games, with notes when we run out of the theory. Sometimes I prepared news in advance (before the game), sometimes during the game. Or, of course, I am faced with a novelty during the game and need to demonstrate I understand basic ideas of the position.
A sharp draw in Frehch Defence (Gonnosuke vs LydiaBlonde
His move 13. Qbt5!? was a news (at least acording to chessok.com and chesslive.de). It was followed by an interesting strugle, resulted in a draw.
A strugle for the center (learn from Rusa Goletiani!)
Her 11. Bb3!? was a news. I answered with a combination of ideas from few other games, wich I found in databases. I lost, and this game (as the previous one!) could be included in databases, for future users - maybe they will find something better!
French defence - a game of interest for theory
This is the nice one! In the databases, I found 6 games with a position after 12th move of black - and in all of them black win! In analysis (and I am not sure now was it before the game or after it's begining) I found a new idea for white (moves 13 to 16th). And I win! Smart me!
I have no so good memory to can have all this in my head. So, this kind of chess (as like as clasical CC) alow me to crate much beter games, which can be of interest for others too! (And become a parto of "theory".)
lydia makes good points. In the rules of correspondence chess, using reference materials is legal but having others decide your moves for you is not and that includes chess engines as well as other human beings. Sometimes when I can't remember a move in a particular line or I want to try out an opening I am not so familiar with I will look for examples of that opening in my books or online but that is not cheating although I have encountered some players who think it is. I always tell them to direct their complaints to the ICCF since they are the ones who make the rules for distance chess. Online chess sites should use ICCF rules.

spoff> I believe (with no proof of course) that cheating is rampant on fics.
In my last ~250 games on FICS there in only about 3 of them did my opponents play blunder-free games where I had no chance of winning. I play only blitz (2+12), and rapid (G/15, G/20) time controls there and only play registered accounts (since poor sportsmanship, name-calling, etc. mostly comes from unregistered accounts).

On top of that, in the grand scheme of things, is it even that important? Your chess.com rating can't be used anywhere. It doesn't get you a t-shirt or advanced tournament standing.
Oh, no! I wish a T-shirt! Something with "chess.com 2000+" or so! Erik, pleeeease, can't you arange it?
I have purchased a blank white T-shirt, and i am thinking of getting "my chess.com rating is 2700+!" printed on it. [On the back I will maybe also get "I am a chess Grandmaster" printed.]
Does that count as cheating?