Why can an Episcopalian not receive the Eucharist in the Catholic Church?

An Episcopalian friend goes bonkers because he cannot receive the eucharist in a Catholic Church? He says that he has the same beliefs on the eucharist as Catholics and there should be no impediment. How should I explain to him why Episcopalians cannot receive the eucharist in the Catholic Church?

These links should be helpful for understanding why non-Catholics should not take Communion at Mass. If you have any further questions or concerns that are not answered by these links, please contact Catholic Answers directly.
Recommended Reading:
*]Who Can Receive Communion?
Ecclesia de Eucharistia **(Note especially sections 43-46)

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