No it's not illegal to feed Canadian Geese as long as you feed the Canadian Geese proper food that will not harm them.
What is illegal is Killing the Canadian Geese because Canadian Geese are protected by federal law and if you kill Canadian Geese and are caught you could face fines and possible jail time or prison time.
But you can legally feed Canadian Geese when you see them.
Some things that you can feed Canadian Geese are Frozen peas or corn, Cracked Corn, Grapes, Birdseed, rice, oats and Milo.
The Canadian Geese might also eat some bread that you can feed them.