Well, in my country that is illegal and the dog was protected by our government not being abuse and the dog fight may consider as an abusement of the animals. I will not support of betting dog fight because that might the reason for putting in jail. You can bet anything and there is a cockfight that there is no law against that fight that you support to bet. There is a law here in the Philippines about animal welfare.
Here is a link [ Republic Act No. 8485 ]