ST. PAUL, Minn. (AP) — The parents of a gay Minnesota soldier who was killed in Afghanistan say he died to protect rights he didn’t have himself.

Jeff and Lori Wilfahrt spoke at the Capitol Tuesday on behalf of Minnesotans United for All Families. The group is enlisting veterans and their families to help defeat the constitutional amendment to ban gay marriage on November’s ballot.

Andrew Wilfahrt was killed in Afghanistan in 2011. His parents say he enlisted knowing he’d have to hide his sexuality. They say Minnesota voters should follow the lead of the military which lifted its ban on openly gay soldiers in 2011.

U.S. Rep. Tim Walz, a National Guard veteran, also spoke against the amendment. Walz said during his first campaign in 2006 that he supported gay marriage rights.