From the AG's opinion:
And a “peace officer” in Texas for purposes of the
Penal Code is a “a person elected, employed, or appointed as a peace officer under Article 2.12,
Code of Criminal Procedure . . . or other law.” TEX. PENAL CODE § 1.07(36). A “peace officer”
under article 2.12, Code of Criminal Procedure, includes any of the positions listed therein. See
TEX. CODE CRIM. PROC. art. 2.12.
From the Code of Criminal Procedure:
Art. 2.12. WHO ARE PEACE OFFICERS. The following are peace officers:
(1) sheriffs, their deputies, and those reserve deputies who hold a permanent peace officer license issued under Chapter 1701, Occupations Code;
(2) constables, deputy constables, and those reserve deputy constables who hold a permanent peace officer license issued under Chapter 1701, Occupations Code;
(3) marshals or police officers of an incorporated city, town, or village, and those reserve municipal police officers who hold a permanent peace officer license issued under Chapter 1701, Occupations Code;
(4) rangers, officers, and members of the reserve officer corps commissioned by the Public Safety Commission and the Director of the Department of Public Safety;
(5) investigators of the district attorneys', criminal district attorneys', and county attorneys' offices;
(6) law enforcement agents of the Texas Alcoholic Beverage Commission;
(7) each member of an arson investigating unit commissioned by a city, a county, or the state;
(8) officers commissioned under Section 37.081, Education Code, or Subchapter E, Chapter 51, Education Code;
(9) officers commissioned by the General Services Commission;
(10) law enforcement officers commissioned by the Parks and Wildlife Commission;
(11) airport police officers commissioned by a city with a population of more than 1.18 million located primarily in a county with a population of 2 million or more that operates an airport that serves commercial air carriers;
(12) airport security personnel commissioned as peace officers by the governing body of any political subdivision of this state, other than a city described by Subdivision (11), that operates an airport that serves commercial air carriers;
(13) municipal park and recreational patrolmen and security officers;
(14) security officers and investigators commissioned as peace officers by the comptroller;
(15) officers commissioned by a water control and improvement district under Section 49.216, Water Code;
(16) officers commissioned by a board of trustees under Chapter 54, Transportation Code;
(17) investigators commissioned by the Texas Medical Board;
(18) officers commissioned by:
(A) the board of managers of the Dallas County Hospital District, the Tarrant County Hospital District, the Bexar County Hospital District, or the El Paso County Hospital District under Section 281.057, Health and Safety Code;
(B) the board of directors of the Ector County Hospital District under Section 1024.117, Special District Local Laws Code;
(C) the board of directors of the Midland County Hospital District of Midland County, Texas, under Section 1061.121, Special District Local Laws Code; and
(D) the board of hospital managers of the Lubbock County Hospital District of Lubbock County, Texas, under Section 1053.113, Special District Local Laws Code;
(19) county park rangers commissioned under Subchapter E, Chapter 351, Local Government Code;
(20) investigators employed by the Texas Racing Commission;
(21) officers commissioned under Chapter 554, Occupations Code;
(22) officers commissioned by the governing body of a metropolitan rapid transit authority under Section 451.108, Transportation Code, or by a regional transportation authority under Section 452.110, Transportation Code;
(23) investigators commissioned by the attorney general under Section 402.009, Government Code;
(24) security officers and investigators commissioned as peace officers under Chapter 466, Government Code;
(25) officers appointed by an appellate court under Subchapter F, Chapter 53, Government Code;
(26) officers commissioned by the state fire marshal under Chapter 417, Government Code;
(27) an investigator commissioned by the commissioner of insurance under Section 701.104, Insurance Code;
(28) apprehension specialists and inspectors general commissioned by the Texas Juvenile Justice Department as officers under Sections 242.102 and 243.052, Human Resources Code;
(29) officers appointed by the inspector general of the Texas Department of Criminal Justice under Section 493.019, Government Code;
(30) investigators commissioned by the Texas Commission on Law Enforcement under Section 1701.160, Occupations Code;
(31) commission investigators commissioned by the Texas Private Security Board under Section 1702.061, Occupations Code;
(32) the fire marshal and any officers, inspectors, or investigators commissioned by an emergency services district under Chapter 775, Health and Safety Code;
(33) officers commissioned by the State Board of Dental Examiners under Section 254.013, Occupations Code, subject to the limitations imposed by that section;
(34) investigators commissioned by the Texas Juvenile Justice Department as officers under Section 221.011, Human Resources Code; and
(35) the fire marshal and any related officers, inspectors, or investigators commissioned by a county under Subchapter B, Chapter 352, Local Government Code.
But wait, there's more!
Article 2.121 Lists "Railroad Peace Officers" who are Texas Peace Officers
Article 2.122 specifically states that "Special Investigators" are not peace officers but have powers of arrest, search, and seizure under the laws of Texas for felonies only. "Special Investigators" are the Feds: FBI, Secret Service, etc.
Reading further on down it appears peace officers from adjoining states have the same duties, powers, and immunities as Texas peace officers when the other states' officers are performing certain official acts.
Up to 50 employees of the Texas and Southwest Cattle Raisers Associations may be appointed as Special Rangers by the DPS with the authority of Texas peace officers to make arrests and to prevent and abate cattle theft...except that they can't write traffic citations.
Officers commissioned by the Kickapoo and Alabama-Coushatta tribal governments appear to be Texas peace officers. They may arrest on their own authority anyone violating Texas law within the boundaries of the reservation, and may exercise peace officer authority outside the reservation when summoned by or assisting another law enforcement agency.
a school marshal may:
(1) make arrests and exercise all authority given peace officers under this code, subject to written regulations adopted by:
(A) the board of trustees of a school district or the governing body of an open-enrollment charter school under Section 37.0811, Education Code;
(B) the governing body of a private school under Section 37.0813, Education Code; or
(C) the governing board of a public junior college under Section 51.220, Education Code; and
(2) only act as necessary to prevent or abate the commission of an offense that threatens serious bodily injury or death of students, faculty, or visitors on school premises.
(1) and (2) seem in conflict to me, but in any case I guess a school marshal is a peace officer.
You can go look for yourself here: