<p>I've been trying to consider how Row Level Security could be implemented with the Entity Framework.  The idea is to have a database agnostic means that would offer methods to restrict the rows coming from the ObjectContext.</p>

<p>Some of my inital ideas have involved modifying the partial classes created by the EDMGEN tool and that has offered some limited support.  Users are still able to get around this solution by using their own eSQL statements and a QueryObject.  </p>

<p>I've been looking for a comprehensive solution that would exist above the database providers so that it would remain agnostic.</p>

The place where you add security really depends on who you're trying to secure against.
If, for example, you were securing a web site, then adding the filtering at the context level would be sufficient, because the "users" in this case are on the web site. They have no choice but to go through your context, since you would write the application entirely against the context.
In your case, it sounds like the "users" you're trying to secure against are developers. That's quite a bit more difficult. If the developers don't have access to make modifications to the database itself, then you'll have to put the security at the database level. No amount of eSQL access is going to be able to get around the database saying "no".