You may be stopped and depending on your charges be detained ( like in immigration detention center detained ). Go to an attorney before traveling or applying for Naturalization.
This is not legal advice and a client attorney relationship is not created. You should not rely solely on the information provided in this page as every case is different and laws are in a constant state of change.
It depends what substance, how much, and other information.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.