On March 27, 2007, Governor Rick Perry signed Senate Bill 378 into law, making Texas a "Castle Doctrine" state which came into effect September 1, 2007.[240] Residents lawfully occupying a dwelling may shoot a person who "unlawfully, and with force, enters or attempts to enter the dwelling", or who removes or attempts to remove someone from that dwelling, or who commits or attempts to commit a "qualifying" felony such as burglary, arson, rape, aggravated assault, robbery or murder. In addition, a shooter who has a legal right to be wherever he/she is at the time of a defensive shooting has no "duty to retreat" before being justified in shooting; the "trier of fact" may not consider whether the person retreated when deciding whether the person was justified in shooting.

Gov. Perry also signed H.B. 1815, a bill that allows any Texas resident to carry a concealed handgun in the resident's motor vehicle without a CHL or other permit.[241] Chapter 46, Section 2 of the Penal Code states that it is in fact not "Unlawful Carry of a Weapon" for a person to carry a weapon while in a motor vehicle they own or control, or to carry while heading directly from the person's home to that car. However, lawful carry while in a vehicle requires these three critical qualifiers: (1) the gun must be concealed; (2) the carrier cannot be involved in criminal activities; and (3) the carrier cannot be a member of a criminal gang.[242][243]

Texas has no laws regarding possession of handguns, shotguns, or rifles by persons 18 years or older without felony convictions; a rifle, shotgun, or other long-barreled firearm may be carried openly, however, a permit to carry is required for handguns (issued only to those 21 and older), and they must be concealed.
However, to PURCHASE a handgun, you must be 21 or older in every state, per federal law in order to purchase from a federally licensed dealer. You can, however, purchase a handgun at 18 in a private sale.