Since this is an immigration classification intended to promote educational and cultural exchange, there is an expectation that J-1 status holders will return home to apply the knowledge and skills gained in the U.S. As a result, there are certain restrictions placed upon individuals who have previously been in the U.S. in J-1 status. These restrictions apply to individuals who have completed their previous J program and seek to return to begin a new program as either a research Scholar or as a professor.
Twelve-month bar: a person who previously held J status in any category other than short term scholar for more than six months cannot begin a new J-1 program in either the Research Scholar or Professor classification until the individual has been outside the U.S. for twelve months or more. (please note, this bar does not prevent someone who is actively engaged in a J program from transferring his/her J-1 sponsorship to the Catholic University.
Two-year bar: a person who previously held J-1 status (regardless of how long he/she was actually present in the U.S.) as either a Professor or Research Scholar cannot return to the U.S. to begin a new J-1 program as either a Research Scholar or as a Professor until he/she has been outside of the U.S. for two years. This is a different requirement from the two-year home country physical presence requirement that attaches to some J status holders.
The J-1 Two-year Home Country Physical Presence Requirement, click link.