If I am conveying property to Person A can I reserve an easement to Person B to cross Person A’s property. Does it matter that Person B is not a party to the conveyance.
And you response was "Yes".
What law applies here?
As you've already been told; Yes, you can convey an easement across property YOU OWN. You must do it before the property is sold, and you should disclose the easement to person "A".
Provided that the easement does not violate any law or ordinance, there is no law I know of that prevents you from granting the easement.
You may not be legally required to disclose the easement, as long as it is filed and available during a timely search of the titles.
It may be fraud or misrepresentation if you attempted to hide the easement from party "A".