You need to retain an experienced immigration lawyer to review all the facts, including the documents pertaining to his conviction and immigration history, and advise you accordingly.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship.
I agree with collegue: you need to bring all the conviction documents to an immigration attorney who is experienced with immigration consequences of criminal convictions. Your boyfrined might be an "aggravated felon" (lawyer must review case) and barred from coming back to the U.S. for a LONG time. If an aggravated felon is caught re-entering, the prison sentences arte up to 20 years.
Unfortunately it is doubtful that your boyfriend will ever be able to return to the U.S. Since he has a conviction for sale of a controlled substance he was most likely removed as an aggravated felon and is permanently inadmissible to the United States not only due to the controlled substance conviction, but because an consular and/or immigration officer will have reason to believe that he is a trafficker in controlled substances. Marrying him will to change these facts.
While written by an attorney who is a Florida Bar Certified Specialist in Immigration and Nationality Law, the statements herein should not be construed as legal advice. No attorney/client relationship has been created without a formal consultation with the attorney and the attorney has agreed to accept your case.