I've never heard of anybody being denied the right of owning a gun simply because they have a restraining order against them. A convicted felon is a conviction, and the mentally unstable are usually under the care of somebody else either an institution, a care giver or parent.
However if you are just an average ordinary American not convicted of anything, your constitutional rights are guaranteed to you.
Actually, a restraining order CAN get your guns taken away.
Domestic Violence Offender Gun Ban - Wikipedia, the free encyclopedia
The
Domestic Violence Offender Gun Ban often called "
the Lautenberg Amendment" ("Gun Ban for Individuals Convicted of a Misdemeanor Crime of Domestic Violence",
Pub.L. 104–208,
[1]18 U.S.C.§ 922(g)(9)[2]) is an amendment to the Omnibus Consolidated Appropriations Act of 1997 enacted by the
104th United States Congress in 1996, which bans access to firearms by people convicted of crimes of domestic violence. The act is often referred to as "the Lautenberg Amendment" after its sponsor, Senator
Frank Lautenberg (D - NJ).
The act bans shipment, transport, ownership and use of guns or ammunition by individuals convicted of
misdemeanordomestic violence,
or who are under a restraining (protection) order for domestic abuse that falls within the criteria set by 18 U.S.C. § 922(g)(8). The act also makes it unlawful to knowingly sell or give a firearm or ammunition to such persons.