It was my understanding that they were legal to own, but illegal to carry here.
ETA: From Texas PC Ch. 46.01
Sec. 46.01. DEFINITIONS. In this chapter:
(1) "Club" means an instrument that is specially designed, made, or adapted for the purpose of inflicting serious bodily injury or death by striking a person with the instrument, and includes but is not limited to the following:
(A) blackjack;
(B) nightstick;
(C) mace;
(D) tomahawk.
(2) "Explosive weapon" means any explosive or incendiary bomb, grenade, rocket, or mine, that is designed, made, or adapted for the purpose of inflicting serious bodily injury, death, or substantial property damage, or for the principal purpose of causing such a loud report as to cause undue public alarm or terror, and includes a device designed, made, or adapted for delivery or shooting an explosive weapon.
(3) "Firearm" means any device designed, made, or adapted to expel a projectile through a barrel by using the energy generated by an explosion or burning substance or any device readily convertible to that use. Firearm does not include antique or curio firearms that were manufactured prior to 1899 and that may have, as an integral part, a folding knife blade or other characteristics of weapons made illegal by this chapter.
(4) "Firearm silencer" means any device designed, made, or adapted to muffle the report of a firearm.
(5) "Handgun" means any firearm that is designed, made, or adapted to be fired with one hand.
(6) "Illegal knife" means a:
(A) knife with a blade over five and one-half inches;
(B) hand instrument designed to cut or stab another by being thrown;
(C) dagger, including but not limited to a dirk, stilletto, and poniard;
(D) bowie knife;
(E) sword; or
(F) spear.
(7) "Knife" means any bladed hand instrument that is capable of inflicting serious bodily injury or death by cutting or stabbing a person with the instrument.
.
.
(11) "Switchblade knife" means any knife that has a blade that folds, closes, or retracts into the handle or sheath, and that:
(A) opens automatically by pressure applied to a button or other device located on the handle; or
(B) opens or releases a blade from the handle or sheath by the force of gravity or by the application of centrifugal force.
Now, from PC 46.05:
Sec. 46.05. PROHIBITED WEAPONS. (a) A person commits an offense if he intentionally or knowingly possesses, manufactures, transports, repairs, or sells:
(1) an explosive weapon;
(2) a machine gun;
(3) a short-barrel firearm;
(4) a firearm silencer;
(5) a switchblade knife;
(6) knuckles;
(7) armor-piercing ammunition;
(8) a chemical dispensing device; or
(9) a zip gun.
(b) It is a defense to prosecution under this section that the actor's conduct was incidental to the performance of official duty by the armed forces or national guard, a governmental law enforcement agency, or a correctional facility.
(c) It is a defense to prosecution under this section that the actor's possession was pursuant to registration pursuant to the National Firearms Act, as amended.
(d) It is an affirmative defense to prosecution under this section that the actor's conduct:
(1) was incidental to dealing with a switchblade knife, springblade knife, or short-barrel firearm solely as an antique or curio; or
(2) was incidental to dealing with armor-piercing ammunition solely for the purpose of making the ammunition available to an organization, agency, or institution listed in Subsection (b).
(e) An offense under this section is a felony of the third degree unless it is committed under Subsection (a)(5) or (a)(6), in which event, it is a Class A misdemeanor.