Sec. 545.057. PASSING TO THE RIGHT. (a) An operator may pass to the right of another vehicle only if conditions permit safely passing to the right and:
(1) the vehicle being passed is making or about to make a left turn; and
(2) the operator is:
(A) on a highway having unobstructed pavement not occupied by parked vehicles and sufficient width for two or more lines of moving vehicles in each direction; or
(B) on a one-way street or on a roadway having traffic restricted to one direction of movement and the roadway is free from obstructions and wide enough for two or more lines of moving vehicles.
(b) An operator may not pass to the right by leaving the main traveled portion of a roadway except as provided by Section 545.058.

Sec. 545.058. DRIVING ON IMPROVED SHOULDER. (a) An operator may drive on an improved shoulder to the right of the main traveled portion of a roadway if that operation is necessary and may be done safely, but only:
(1) to stop, stand, or park;
(2) to accelerate before entering the main traveled lane of traffic;
(3) to decelerate before making a right turn;
(4) to pass another vehicle that is slowing or stopped on the main traveled portion of the highway, disabled, or preparing to make a left turn;
(5) to allow another vehicle traveling faster to pass;
(6) as permitted or required by an official traffic-control device; or
(7) to avoid a collision.
(b) An operator may drive on an improved shoulder to the left of the main traveled portion of a divided or limited-access or controlled-access highway if that operation may be done safely, but only:
(1) to slow or stop when the vehicle is disabled and traffic or other circumstances prohibit the safe movement of the vehicle to the shoulder to the right of the main traveled portion of the roadway;
(2) as permitted or required by an official traffic-control device; or
(3) to avoid a collision.
(c) A limitation in this section on driving on an improved shoulder does not apply to:
(1) an authorized emergency vehicle responding to a call;
(2) a police patrol; or
(3) a bicycle.


http://www.statutes.legis.state.tx.us/Docs/TN/htm/TN.545.htm

The only reason we pass on the right is because there are too many people who think that the far left lane is the cruising lane, where you just put on cruise control 3 miles below the speed limit and pull out your cell phone. If you are in the left lane and going the same speed as the people to the right of you, it is your responsibility to move over so the rest of us don't have to navigate around your slow ass in the PASSING lane.