Talk to the dog's owner and let them know your concerns. Tell them you'll be reporting your concerns to authorities. German Shepherds can handle the cold if they have shelter but being tied up continuously is neglect and abuse.
I'm not sure of the legality but if it's chained and continuously barking you should call animal control. You can also go on Facebook.look for Rescue. Many of them will check the dog out and help.
Also it matters which municipality its in. Each town has slightly different laws for tie outs and temperature ranges
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