New Delhi, July 21 -- In a striking example of how immigration hurdles can impact even top leadership roles, Collie Greenwood, the CEO of one of America's largest public transit systems, has stepped down after his work permit expired, before his green card could be processed, Newsweek reported.

Greenwood, a Canadian citizen and head of the Metropolitan Atlanta Rapid Transit Authority (MARTA), was forced into early retirement after his Employment Authorisation Document (EAD) lapsed in June. Despite being in the US legally and awaiting his green card, he was no longer permitted to work under current immigration laws.

According to MARTA's official statement, Greenwood's green card approval is imminent, but the gap in documentation left him...