I'm not an attorney and certainly have no legal expertise, but here's my 2 cents.
Laws vary country to country, but in the US, this is a tangled web at best.
As I understand the fair use provision, some courts have said it's ok for consumers to make a copy for their own use, but these same courts have rendered a decision that makes owning and using the tools to make such copy, illegal, at least in the US.
On the one hand, I can't imagine a movie studio going after an individual who has legally purchased a studio movie and made a copy on his/her hdd to use in his/her own home.
On the other hand, I wouldn't sell copies on the street corner.
I would do nothing to call attention to myself.
Right or wrong, consumers do not have deep enough pockets to go up against a movie studio.
And no, there is no way to determine if a dvd has been viewed vs.copied.
The very same laser on a ODD reads the disc whether it is being "viewed" or "ripped".