A student who has been convicted of a drug-related felony or misdemeanor that took place while s/he was receiving Federal student aid shall not be eligible to receive federal student aid (including any grant, loan, or work assistance) during the period beginning on the date of such conviction and ending after the interval specified below:

If convicted of an offense involving the possession of a controlled substance:

Ineligibility period is:

First offense: 1 year
Second offense: 2 years
Third offense: Indefinite

If convicted of an offense involving the sale of a controlled substance:

Ineligibility period is:

First offense: 2 years
Second offense: Indefinite
A student whose eligibility has been suspended may resume eligibility before the end of the ineligibility period if the student satisfactorily completes a drug rehabilitation program that is approved by the U.S. Secretary of Education.

More Information regarding drug convictions can be found here (pdf).