Board Thread:Show-Related Questions and Answers/@comment-5989182-20140321215739/@comment-5106672-20140330205358

Regina indirectly told Robin Hood in 3x13 she learend how to make a Sleeping Curse herself in Storybrooke (in 2x08). She said the Sleeping Curse she used on Snow White came from Maleficient, but now she had learned to do it herself, so she didn't know how to do it when she needed it on Emma.

Besides, magical items that were carried to Storybrooke still had their properties* before magic was brought altogether, which includes Daniel's ring, Regina's potion ingredients, the True Love potion and, of course, the poisoned apple. That's why she could use it on Emma (actually Henry) before magic was brought to Storybrooke. They simply could not make new magic or use spells because they themselves were not magical anymore (like Dwarves were not Dwarves anymore, Fairies weren't either and so on).


 * This would seem to exclude the Dark One's dagger, but the dagger itself is not really magical, it has only connection with the then-non-magical Dark One's powers.