Cards and 50/50 are not against any USBC rules....however, IF..big word, if they are against any local/state gaming laws, then, you have violated local laws, and one can make a case using the old...'actions unbecoming the league'...
In AZ, gaming laws are not super tough and IF, again, if some of the money goes to a 'non-profit' organization ( leagues ) then it is not a gaming problem because a non-profit organization can run fund raisers such as those.
IN AZ, you'd have to check your state/local laws about gaming or gambling.
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az guy aka: R & L Bowlers Pro
rlbowlerspro@cox.net