A female plane passenger took to Reddit this week to share a horrifying photo of a stranger performing a rude act during her flight. 

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An apparent step-up of receipt and shopping bag checks at Walmart has sparked customer complaints, raising concerns about shoppers' rights."It was not a request, it was a demand," said Penny Rintoul of Vaughan, Ont., about a recent receipt check just before she exited Walmart with her purchases. She said her local Walmart increased its checks in the spring."It's very angering and demeaning." The Canadian Civil Liberties Association (CCLA) said it's investigating the practice of retailers doing routine security checks at the exit, concerned that the way they're conducted may jeopardize customers' rights. Michael Bryant, CCLA's executive director and general counsel, said retailers should get consent before checking receipts or bags. And if no consent is provided, he said, customers are under no obligation to comply. "Their right is to say, 'Thanks, but no thanks,' and walk away," said Bryant."Some people feel strongly about their privacy and, in fact, the way our laws work, that privacy and liberty is protected."In a 2016 ruling on a case involving a suspected shoplifter, an Ontario Superior Court judge wrote that a retailer can detain a suspect if there are reasonable grounds, but - even then - it would have to get consent to do a search. Walmart didn't directly address questions from CBC News about customers' rights including what happens if shoppers refuse receipt checks. The retail giant also didn't say if it has stepped up its security checks."To assist in our efforts to manage costs and offer everyday low prices, customers may be asked to show their receipts as they exit our store to ensure the checkout process went smoothly," said Walmart Canada spokesperson Adam Grachnik in an email.CBC News interviewed several customers who said they weren't "asked," and instead felt pressured to comply.Paula Fletcher of Renfrew County, Ont., said that in August, a Walmart employee watched as she scanned her groceries at self-checkout, and then insisted on inspecting her receipt and shopping bag. "She did not make it an option," said Fletcher. "I don't like being treated as a criminal," she said. "If they don't trust us, they shouldn't have self-checkout." Walmart's recent addition of self-checkout machines appears to be a driving force behind receipt checks. In response to customer complaints on social media, the retailer has replied repeatedly that it's doing the checks to ensure the self-checkout process "went smoothly" and that all items have been scanned. Studies suggest that stores adding self-checkouts can experience more theft because thieves believe the risk of getting caught not scanning items is low.Amy Fraser of Sydney Mines, N.S., said she has experienced frequent receipt and occasional shopping bag inspections in the past five months at Walmart, both after using self-checkout and checking out with a cashier. She said she reached her limit last month when a Walmart employee demanded to check her receipt, just as she prepared to feed her baby before exiting. "He's like pouncing, 'You have your receipt?'" said Fraser. "I just [felt] like walking out and being like, 'No, no, call the cops on me.'"So what happens if a retailer calls the cops? Toronto security consultant James Reese said a retailer needs to have evidence of theft for police to take action. "If they did not see you take something, they cannot come after you just for refusing to show your bags or receipt," he said. In the 2016 case involving the suspected shoplifter, the judge also wrote that "if a store owner is mistaken and no theft has occurred, their detention of a customer makes them liable for … false imprisonment."However, shoppers rejecting receipt checks do risk being banned from the store, said Reese."That's within the merchant's prerogative."What about Costco?Retail giant Costco also checks customers' receipts. However, Costco customers are required to sign up for a membership, which means they may have provided consent - depending on how clearly the rules are laid out, said CCLA's Bryant."They need to tell people about it."Costco didn't reply to requests for comment, but CBC News found its policy on its website in the "membership conditions" section. It says customers are required to show receipts to ensure that "you have been properly charged for your purchases" and to maintain accurate inventory control.At Walmart, there's no membership requirement and customers interviewed said they saw no in-store warnings that they'd be checked. Last week, CBC News did discover signs at several Toronto-area Walmarts which stated, "Please have Receipt ready for Proof of Purchase." But a Toronto criminal lawyer argues that's not good enough. "Just because there's a sign doesn't mean that someone's read it or understood it," said Anthony Moustacalis."Consent does need to be fully informed," he said. "That generally means that you need to know that you have a right to refuse."There's no question that shoplifting is a problem for retailers, especially when it comes to self-checkout. But retailers still need to play by the rules, even when tackling emerging technologies, said Bryant. "New technology should never mean giving up your rights."