"You may not touch the cake!"
Translation:Du må ikke røre kagen!
In this context 'røre ved' and 'røre' is not necessarily the same thing. 'Røre ved' would literately mean don’t touch the cake, whereas ‘røre’ could (and probably does) figuratively mean don’t eat the cake. However, ‘røre’ can still be used literately to mean the same thing as ‘røre ved’ – that is ‘ved’ is optional. Therefore, it depends – are you not allowed to psychically touch the cake because you would mess up the beautiful frosting then you can use ‘røre’ or ‘røre ved’, or does this person know your terrifying history of eating entire cakes then you should use ‘røre’. :) That is, when you are using ‘røre’ as ‘consume’ you would leave out ‘ved’. You can always leave out ‘ved’ regardless of the various meaning of ‘røre’, and as in this example sometimes, it is (slightly) wrong to use ‘ved’.