A person is denied Communion because they are living in a state of unrepenyant sin...adultry
Men don't annul a marriage...they investigate the conditions concerning the marriage and make a judgement as to whether or not it was properly entered into. Was one or the other previously married, are they related, were they physically able to consummate the marriage, were they both open to having children, were there and legal situations present which would prevent their union, were either of them coerced into the marriage....it is, or always should be, a simple judgement as to whether or not the marriage was properly conducted.
If men don't annul marriage, how does their interaction/judgement result in it being nullified? How does their interaction at the ceremony cement a marriage in the first place? What is the difference in a marriage by the Justice of the Peace and one conducted by a priest if they both use the same phraseology? Isn't the true marriage conducted within the hearts of those being married?