TexasCHLforum.com

In addition tot he post from TXInvestigator, I thought I would add in the following from the Parks and Wildlife Code, which used to limit game wardens:

§ 11.019. EMPLOYEES AS PEACE OFFICERS. (a) The director
may commission as peace officers any of the employees provided for
in the general appropriations act.
(b) Law enforcement officers commissioned by the director
have the same powers, privileges, and immunities as peace officers
coextensive with the boundaries of this state.
(c) Law enforcement officers commissioned by the director
have the same authority as a sheriff to arrest, serve criminal or
civil process, and require aid in serving criminal or civil process
coextensive with the boundaries of this state.
(d) A law enforcement officer commissioned by the director
may arrest without a warrant any person in this state found in the
act of violating any law.


So, yes, they can arrest for anything and can help when the local police are non-existent or busy. Normally, most state officers, including DPS, game wardens, and TABC agents, work as back-up for local officers, with the county Sheriff's Office handling the primary duties when there are no local police.

As for the PI instead of a DWI charge, it was probably done for a couple reasons. If the GW thought he had the drug case, he would probably have gotten lazy and not done the paperwork or testing for the DWI case. He may not have even had all of the forms needed for the DWI, which is a lot of specific forms that are not used for anything else. Then, when the drug case folded up, he went the easiest way to cover himself, with a PI arrest that is enough to avoid releasing the car and suspect right away. Some guys just don't understand that it is perfectly okay to say "I'm sorry, I will get you back out to your car and you are free to go".