I was married in a Justice of the Peace’s office… in Vegas… in another denomination… but I’m Catholic… may I go to Holy Communion?
Remember, marriage is a sacrament of the Church and is a public institution.  To be married outside the Church is really not an act “in union” with the Church… consequently, it is appropriate to refrain from receiving Holy Communion until such a time as your marriage can be “blessed” in the Church.

How would I go about doing this?
Contact the Cathedral offices to begin marriage preparation.  It’s quite possible this process of “validating” your marriage may be easier than you think.  Ordinarily, however, some elements of catechesis and formation are called for.  Upon completion, you could even have “church wedding” within a special Mass.  Again, contact the Cathedral offices for more information.

I’m not Catholic but I was married previously to another person… I’m now married to a Catholic who is concerned about his/her standing within the Catholic Church.  I’m told that I would need to investigate the possibility of an annulment -- in the Catholic Church, no less – with my first spouse.  Now why is this?
This is understandably a difficult and confusing circumstance, but the reasons for this are rooted first of all in the integrity of a promise made.  Presumably, you made vows, did you not?  Those vows, most likely, were pronounced “until death do we part.”  Again… we must presume that you meant those words when you said them, unless there was some defect in your consent to that first marriage (hence, we take a look at the courtship and circumstances in which you entered the marriage to begin with).

Also, it is baptism that brings us into God’s Kingdom and makes us His children… it’s the one thing that all Christians share, is it not?  Consequently, some authority must weigh in on the matter, for marriage is something that affects civilized society… it’s not just a “Catholic” thing!  Best to discuss this with a priest or pastoral associate directly and to make some initial assessment.