These illegal aliens knew this was temporary, deferred action from their deportation only, when they signed up.

1) Temporary: continuing for a limited amount of time; not permanent
http://www.learnersdictionary.com/definition/temporary

2) Deferred: put off or delayed
http://www.yourdictionary.com/deferred

3) The Deferred Action for Childhood Arrivals (DACA) allowed some individuals who entered the country illegally as minors to receive a renewable two-year period of *deferred action from deportation*