I depends on the country you live on.
If backup copies aren't allowed, you're not allowed to download a rom, even if you own the original card and you don't use them at one time.
If backup copies are allowed then you are allowed to have a backup - however, in most countries you are not allowed to download it but have to copy it for yourself. (I just don't know how anyone will notice, since you could have borrowed a rom reader from a friend

)
In some countries the copyright is completely ignored. These are the countries where all the warez server keep alive for a loooong time...