He should NOT travel.
He should meet with an attorney to discuss his situation.
Franco Capriotti - Senior Immigration Counsel
CAPRIOTTI INTERNATIONAL LAW
firstname.lastname@example.org -- 1-503-803-0055 -- www.capriotti.com
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IMMIGRATION LAW PROFESSOR for 10 years -- LEGAL DISCLAIMER: This answer is offered for informational purposes only. It does not constitute an attorney-client relationship.
There is a serious and significant risk that he will be placed into removal proceedings if he leaves the country and returns. Whether he has a defense would depend on the facts of the case. He should speak with an experienced attorney before considering doing this.
The above is not legal advice. It is general information. I only give legal advice to those who have a retainer agreement with me. You may also seek further information on my website - http://immigrationlawyernewhavenct.com
Depending on the exact criminal charges he was convicted of and drug that he was convicted of possessing, it is possible that he could be placed in removal proceedings as either being inadmissible to enter the U.S. or removable based upon his drug conviction. I strongly suggest that you contact an experienced immigration attorney for a face-to-face consultation and give him/her all of the facts surrounding your arrest. He/she would then be in a better position to analyze your case and advise you of your options.
Legal disclaimer: The answer provided is general in nature and because not all facts are known, it should not be construed as legal advice. The answer does not create an attorney/client relationship. You should speak to an attorney for further information.