^^^ There will obviously be tax implications for legal US poker sites
. But people get way too caught up in thinking the DOJ is in cahoots with the IRS on anything, or vice-versa. They are independent agencies who don't really work together nor do they typically share jurisdiction. DOJ is Justice, IRS is Treasury, and they typically avoid each other and prosecute their own cases.
Anyone who works with the government will tell you that the big agencies are heavily silo'ed and seldom cooperate. This was one of the big lessons learned after 9/11 between the various intelligence and law enforcement agencies, and it still isn't completely resolved.