The ordinances prohibit guns, ammunition and explosives in county government buildings.
It also requires gun stores to implement practices to protect against theft.
That includes the use of security cameras, alarms and physical barriers.
New Castle County Executive Matt Meyer was joined by County Council members and gun safety advocates as he signed the two ordinances into code on Tuesday.
This comes following a recent smash-and-grab burglary at Miller's Gun Center in Wilmington Manor.
Police charged a 14-year-old in that incident.
14-year-old Wilmington boy arrested in Delaware gun store heist linked to other crimes