SPARQL, the W3C standard real Graph QL, where most implementations accept queries direct over http. Have implementations that do role based security depending on the connection. Commercial implementations such as StarDog or Oracle Semantic Network among many others, will allow you to limit certain subsets of your data in many ways, and connect to many other datasources via different translators/mappers.
For the JSON developer though you would need to combine it with a nice JSON-LD formater which is not yet common among implementations.
(I know some of those might not be the same, just throwing in a bunch of names vaguely clustered in my head)