If my husband was arrested trying to come to the US, would he be able to become legal because we are married?

Your question requires an attorney consultation. It is not a simple question that can be answered on this type of forum. There are many factors that would need to be considered and evaluated. What is your status? Are you a U.S. citizen? Legal Permanent Resident? Undocumented? Was he deported or just sent back to Mexico. Since we do not have all the facts, it is impossible to give a meaningful answers. I suggest that you contact an experienced immigration attorney for a face-to-face consultation and give him/her all of the facts surrounding your husband's situation. (S)he would then be in a better position to analyze his case and advise you of your options.