MMM thats a hard one,
Luckily cody who loves scratching does limit this activity to his scratchy posts (or the iron board which now has a ripped to shreds cover
, also he has been known to reach up and happily use a thigh ... he esp likes jeans to sharpen his claws on LOL)
why can the sticky paws not be used on leather ?? did it give a reason ?
Have you plenty of scratch posts / activity tree etc for them to do this on ?
I'd start cutting their front paw claws on a regular basis, prob every 1 -2 weeks ... codys can be razor sharp in a couple of days after he gets his done.
Scratching is a form or marking their territory and i recently learned they have scent glands in their front paws so perhaps you should try a feliway diffuser (synthetic feline pheramones) this may help , you get the spray aswell but i cant imagine it would be a good idea to spray that on leather.
you could also get a water mist spray bottle and spray them every time they do it till they hopefully get the idea this is not acceptable behaviour.