A person whose application for a green card is still pending might be able to work legally in the United States by filing federal form I-765, according to US-Immigration.com. One can file the application for employment authorization documents along with, or after, filing Form I-485 for adjustment of immigration status.
The U.S. Citizenship and Immigration Services generally issues work permits valid for one year, explains US-Immigration.com. An immigrant can work with the work permit until USCIS approves or rejects the green card application. Once USCIS approves the application and issues the green card, there is no longer a need for the work permit, as a green card entitles a person to work legally in the United States.