This paper proposes a novel approach to let consumers share data from their existing web accounts and devices easily, securely, and with fine granularity of control. Our proposal is to have our personal virtual assistant be responsible for sharing our digital assets. The owner can specify fine-grain access control in natural language; the virtual assistant executes access requests on behalf of the requesters and returns the results, if the requests conform to the owner's access control policies. Specifically, we allow a virtual assistant to share any ThingTalk command--an event-driven task composed of skills drawn from Thingpedia, a crowdsourced repository with over 200 functions currently. Access control in natural language is translated into TACL, a formal language we introduce to let... users express for whom, what, when, where, and how ThingTalk commands can be executed. TACL policies are in turn translated into SMT (Satisfiability Modulo Theories) formulas and enforced using a provably correct algorithm. Our Distributed ThingTalk Protocol lets users access their own and others' data through their own virtual assistant, while enabling sharing without disclosing information to a third party. The proposed ideas have been incorporated and released in the open-source Almond virtual assistant. 18 of the 20 users in a study say that they like the concept proposed, and 14 like the prototype. We show that users are more willing to share their data given the ability to impose TACL constraints, that 90% of enforceable use cases suggested by 60 users are supported by TACL, and that static and dynamic conformance of policies can be enforced efficiently.