Exporting part of normal trading
Jack Murphy owns Jack Murphy Jewellers, an independent family-run business based on Hill Street in Newry.
He said selling to the EU - effectively exporting - was part of every day life for traders in the city.
And Mr Murphy, who also has a shop in Dundalk, said he believes leaving the EU would be detrimental to both traders and shoppers in Newry.
The businessman, who is also the chairman of Newry City Centre Management, said: "Newry is a bit different from somewhere like Birmingham or even Belfast. We definitely do not want to go back to the past of customs clearances that we went through years ago. If you come out of the EU you would have that.
"If you are asking businesses here 'do you export?', they would probably say no as the border is just six or seven miles away," he added.
"Businesses here are selling to people from Dundalk every day but when most people think about exports, they think of selling to China or somewhere in the Middle East."
And he said the UK "must stay in".
He continued: "It would have a huge impact on the city if we left the EU. The last thing we need is to make it harder for people to come into Newry and make it easier for people in Dundalk to decide to go to Dublin instead. We have got to work harder to get people to come north to shop.
"We need to make sure the people of Dundalk, Belfast and Lisburn realise that Newry is a good town."
When asked if he thought leaving the EU would benefit business owners who felt bound by strict EU regulations, he said: "We are old enough and smart enough to remember the stupid laws before the EU came in. There were a lot of silly decisions made in Westminster as well as in Europe. We are inclined to forget things in the past.
"People flow back and forth between Dundalk and Newry and exporting here is part of normal every day trading. If there are border checks put in place, it would put people off shopping here. They wouldn't want the hassle of it."