I have managed big box retail stores for three different large retailers and they all had virtually identical corporate rules on shoplifting:
(1) Employee could not stop the individual, only observe and call management
(2) Person was asked by management if they would like to pay for the item they had concealed
(3) Person was not asked to stop until they had passed the register lanes
(4) At no time was the person held, grabbed or otherwise physically detained, if they cooperated you could escort them to an office or other place to await the police
(5) If they continued to leave the building, you allowed them to do so and just took down their tag number for the police
So basically, if someone wanted to steal from you and knew your corporate policy they could do so blatantly, ignore your command to halt and just walk out the building. By the time the police arrived they would be long gone and as catching a shoplifter is never that high on the police list of priorities they were basically home free.
Rinse, repeat, profit.