[Tantumergo]

"Why are people desiring conversion held to Catholic doctrines on marriage when they were not Catholic nor married Catholic in the first place?"

Because they are not just "Catholic doctrines" on marriage - it is Divine Law and it is immutable.

The Church recognises the validity of marriages among pagans, because although they are not Sacramental marriages, they are covenantal marriages in the eyes of God according to the Natural Law.

The covenant between man and woman in marriage is the most fundamental covenant after God's covenant with creation itself (hence the Genesis account where both covenants are related side by side in the creation narrative) and hence can never be taken lightly:

"What God has joined together, let no man put asunder!"

Nevertheless there are annulment possibilities for non-Catholics becoming Catholic, which are not options for Catholics. Decisions may be arrived at "In favour of the Faith".

[Canticle_of_Deborah]

I understand what you are saying but that is still the Catholic concept of marriage. Non-Catholics might accept all or part of those ideas but among other faiths divorce is still acceptable (although not favorable). This is the part I do not understand. A non-Catholic would not necessarily form a marriage of Catholic intention.

[Canticle_of_Deborah]

The Church recognises the validity of marriages among pagans, because although they are not Sacramental marriages, they are covenantal marriages in the eyes of God according to the Natural Law.

Here's another point. What about atheists?

If a marriage is valid outside the Catholic Church then why the big problem with Catholics marrying in non-Catholic churches?

I'm not trying to be difficult, just looking for some logic which is escaping me thus far.

[topcat54]

it is Divine Law and it is immutable.

So immutable that the RCC has to have these phoney annulment procedures. "What God has joined together ..." Oh, wait a minute, God didn't REALLY join these two together, says man. We found a loophole. Now we can let this philandering ex-husband remarry in the RC church. Just declare ex-cathedra that his first marriage never happened.

Ain't it all convenient when you know what strings to pull?

[Hermann the Cherusker]

Nevertheless there are annulment possibilities for non-Catholics becoming Catholic, which are not options for Catholics. Decisions may be arrived at "In favour of the Faith".

The Petrine Privilege! The Church has the power to dissolve legitimate non-sacramental marriages for a just reason.