AboutHannah Expertise I can answer questions concerning standard doctrines, scriptures, curiousities, Mormon culture and society. I will not respond to debates. I'm sorry, but there are some things that I simply will not answer, not because I don't want to, but there are some things that the LDS people do not discuss casually--it's only talked about within the temple. Though I am a member, I do not believe that anyone could convert anyone to a religion over something as impersonal as the internet. So I won't even try to.
Experience I have been a member of the LDS church for 8 years. Though I'm still a young person, I can answer most things about the church.
Answer The short answer: Sure they can. So long as the Catholic Church is all right with it. I don't know about that part.
The long answer: Even though there is no doctrine against it, and an LDS member wouldn't be excommunicated for marrying a Catholic, it is discouraged. It is discouraged because a fundamental part of The Latter-day Saint religion is eternal marriage. Binding marriage for time ("until death do they part") can be achieved between a Catholic and a "Mormon." However, eternal, everlasting sealed marriage ("for time and all eternity") can only be performed within the temple. Since only baptized members of the church who possess a temple recommend can enter the temple, obviously a Catholic wouldn't be able to enter the temple for the eternal marriage to be performed.
So, it's discouraged, but it is allowed. Is that what you were looking for?