I've heard that in some places such as big cities etc that it's illegal to feed wildlife including squirrels but if you're in a small town or rural area then you likely will not get into trouble for feeding squirrels and other wildlife.
I have a squirrel feeder in my backyard and like to feed the squirrels and watch them in my backyard.
I've never got into trouble and police have seen my squirrel feeder so even if it is illegal you're not likely to really get into any trouble for it.
At worst if it is illegal in your area you'll get a fine but no jail or prison time.
I'm not sure what the fine cost is for illegally feeding wildlife or squirrels but it's probably not really huge.
If you want to feed squirrels at a park or in your own yard then you can do so and you'll probably be okay.
I've also fed squirrels in the park and never got into trouble.