legal question

Technically this would be shoplifting. Also known as "five finger discount" "PIE theft" or "shrinkage".

A couple of popular deterrents are:

Closed circuit television
CCTV monitoring is an important anti-shoplifting technology. Retailers focusing on loss prevention often devote most of their resources to this technology. Using CCTVs to apprehend shoplifters in the act requires full-time human monitoring of the cameras...Good job..? Bad job..?

Sophisticated CCTV systems discriminate the scenes to detect and segregate suspicious behavior (matter of opinion) from numerous screens and to enable automatic alerting. However, the attentiveness of the surveillance personnel may be threatened by false reliance on automatics.

CCTV is more effective if used in conjunction with EAS as the EAS system will alert of a potential shoplifter and the video will provide ample proof to prosecute the shoplifter if the shoplifter is allowed to exit past checkout points or store premises with store merchandise that has not been paid for at final checkout points.

Electronic article surveillance
Electronic article surveillance (EAS) is second only to CCTV in popularity amongst retailers looking for inventory protection. EAS refers to the security tags that are attached to merchandise (ouch) and cause an alarm to sound on exiting the store. Regularly, even when an alarm does sound, a shoplifter walks out casually and is not confronted if no guards are present. This is due to the high number of false alarms, especially in malls, due to "tag pollution" whereby non-deactivated tags from other stores set off the alarm. This can be overcome with newer systems and a properly trained staff. Some new systems either do not alarm from "tag pollution" or they produce a specific alarm when a customer enters the store with a non-deactivated tag so that store personnel can remove or deactivate it so it does not produce a false alarm when exiting the store. However, with tags that are stuck onto merchandise with glue (rather than being superimposed on) the shoplifter can easily scrape off the tag in their pocket.