the irs doesn't give a crap about how you made the money, to be compliant you need to claim any and all income so a tax can be levied.
the pot growers in colorado... they are supposed to claim every penny... the catch is since it is against fed law they can not claim expenses for a deduction like other biz do.
as far as i know there is no fed law against a person making a bet (there may be state laws)
there are fed laws concerning the movement of money
there are fed laws concerning the concealment of funds from their original purpose
there are fed laws concerning the way you structure the deposit or withdrawal of funds to circumvent mandatory reporting
look at it like this.. you take a vacation to the Caribbean, you gamble at one of the casinos and win big. those casinos have no requirement to report your winnings to the US... you bring the money back home and put it in the bank. at tax time it is up to you to declare it as income. if you don't and you get audited the IRS has might think that deposit was income, from what they can only guess? drugs, whoring, gambling? mowing lawns? they don't care. you just need to make them believe its not income.
if you don't think you can do that then the irs will just say it's income and you pay tax and penalty yada yada jail time yada yada.
now let's say you go the extra mile and try to hide this money by putting it in the bank in small deposits over time... you just added structuring and money laundering to your tax avoidance charges