Every US citizen can petition to obtain a green card for their foreign-born spouse. However, if couples have been together less than three years, the green card issued will be a temporary one, valid for only two years. If the couple decides to get divorced before a permanent green card is issued, the process to petition to remove the conditions on residency is very similar whether the couple remains together or not. In the case of a divorced couple, the person petitioning to remain in the US must prove the marriage was valid to begin with and they divorced not due to immigration reasons. This is simply arguing to the court that the couple had a valid marriage in which they shared every part of their lives, and their divorce was completely separate from any immigration considerations. Alternatively, the petitioner could show that their former spouse was abusive in some way or subjected them to extreme mental cruelty. This would require proof in the form of police reports, medical records, and/or sworn testimony of witnesses.