Is decryption/compression still needed to copy a DVD movie using a dual-layer burner?

Correct me if I'm wrong here.

Once upon a time, consumer DVD burners were limited to burning
single-layer DVD's with a capacity of around 5 gb per disk. But
(all?) commercial movie DVD's come on dual-layer disks with a capacity
of up to 9 gb.

So it was never possible for the home computer user to make an exact
copy of a DVD movie in a manner similar to making an exact copy of a
music CD. Instead, the movie had to be decoded (de-crypted) and then
re-compressed (with arguably some loss of detail or resolution) in
order to fit onto a 5 gb blank media. But with the copywrite or
patent or licensing issues surrounding the decoding/decryption
process, there really was no "legal" source for the decoding software
(DVD X-copy being an exception that was eventually killed by the
courts). There are, however, public sources for free-ware decryption
and compression software.

Now then, with the availability of dual-layer DVD burners and
dual-layer media, it should therefore be possible to make a straight
copy of the files on a movie DVD and burn them onto a blank dual-layer
DVD disk and end up with a copy of the movie without the need to seek
out and use decryption/re-compression software.

Is there something I'm missing here, like perhaps some other form of
copy protection or hidden files on the movie DVD that can't be simply
copied to the burn-able disk?