As far as legality you will need to check regulations in your area. Here in WI anything you put down the hole that is not a part of your bait or lure is considered "littering" and you will catch a ticket.
This means oats or corm meal for pannies, whole corn kernels for carp, egg shells to brighten the bottom for spearing visibility, any kind of fish or fish parts that aren't held by a hook, spam, hot dogs, well.....anything. Pretty definitive here. Not that some folks don't do it, I just hate leaving myself open to harassment by a warden; kinda takes the fun out of it.......
Not that I don't think about it......... One way around might be to use a retrievable chum bag. Put your stuff in and lower it down. This would also allow you to shake it from time to time to redistribute the aroma.
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