Presumably the data that you have for the user has some link to the user. Ie
class User< AR::B
class Thing <AR::B
There are a couple of options that come to mind to scope these objects to their owners.
use with_scope. This can help with this area and is available in the docs.
follow the chain of ownership. eg
current_user.things.find( params[:id] )
If the thing does not belong to the user, it will be nil.
Either or both of these should do what you need.
Hope that helps