You can date any age person that you want. That having been said, if dating starts to consist of sex your boyfriend will have a problem since you are a minor. In MT, the age that a person can consent to have sexual activity is 16. Therefore, sexual intercourse with someone who is younger than 16 years old is illegal regardless of the age of the defendant. There are alos other staustes that apply to this situation. Here is a link to a site that will explain further: https://www.ageofconsent.net/states/montana