Can a Person Who is Legally Divorced Go to Confession or Receive Communion Before the Marriage is Annulled?

No. For starters, divorce is not always a sin. But even in instances where it is a sin, absolution for the truly repentant can be attained through confession.

A bigger problem arises when a divorced Catholic without an annulment attempts marriage again. Any such marriage attempted outside the Church is not valid, so, if he lives with his new “spouse” as though they are married, he lives in a state of objective sin.

When a person chooses to live in a state of objective sin, he cannot attain absolution through confession or receive Communion as long as he remains in his present state. The wise thing to do in such a situation is to commit to abstinence until (if ever) his prior marriage is declared null and his current marriage is blessed (convalidated)—then he can go to confession and resume going to Communion.

See this excerpt from the Catechism of the Catholic Church:

Today there are numerous Catholics in many countries who have recourse to civil divorce and contract new civil unions. In fidelity to the words of Jesus Christ—“Whoever divorces his wife and marries another, commits adultery against her; and if she divorces her husband and marries another, she commits adultery”—the Church maintains that a new union cannot be recognized as valid, if the first marriage was. If the divorced are remarried civilly, they find themselves in a situation that objectively contravenes God’s law. Consequently, they cannot receive Eucharistic communion as long as this situation persists. For the same reason, they cannot exercise certain ecclesial responsibilities. Reconciliation through the sacrament of Penance can be granted only to those who have repented for having violated the sign of the covenant and of fidelity to Christ, and who are committed to living in complete continence. (1650)