PENAL CODE
TITLE 10. OFFENSES AGAINST PUBLIC HEALTH, SAFETY, AND MORALS
CHAPTER 46. WEAPONS...
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...(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, stiletto, and poniard;
(D) bowie knife;
(E) sword; or
(F) spear.
The definition of an Illegal Knife in Sec. 46.01(6)(C) still includes "dagger, including but not limited to dirk, stilletto and poniard." That has not changed. None of these types of knives, dagger, etc., are defined in Texas law, but based on case law generally you should assume that a "dagger" covers any double-edged blade. This would include automatic knives with double-edged blades.
Texas law (HB1862) repealed the ban on automatic (switchblade) knives and went into effect on September 1st, 2015
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Sec. 46.02. UNLAWFUL CARRYING WEAPONS. (a) A person commits an offense if the person intentionally, knowingly, or recklessly carries on or about his or her person a handgun, illegal knife, or club if the person is not:
(1) on the person's own premises or premises under the person's control; or
(2) inside of or directly en route to a motor vehicle or watercraft that is owned by the person or under the person's control.
Section 46.02 does not apply to a person who:
(1) is in the actual discharge of official duties as a member of the armed forces or state military forces as defined by Section 437.001, Government Code, or as a guard employed by a penal institution;
(2) is traveling;
(3) is engaging in lawful hunting, fishing, or other sporting activity on the immediate premises where the activity is conducted, or is en route between the premises and the actor's residence, motor vehicle, or watercraft, if the weapon is a type commonly used in the activity;