A U.S. Senator from Missouri is continuing her crackdown on the advantages Alaska Native Corporations enjoy in government contracting.Download AudioSen. Claire McCaskill this week pressed the Small Business Administration to show that rules in place since 2011 are tightening requirements on ANCs and producing better oversight.Since the 1980s, ANCs have won government contracts worth billions of dollars, through a program designed to allow small, minority-owned companies to contract for government work without competition. Other businesses in the program are limited to contracts of up to $4 million. Alaska Native corporations, though, can get sole-source contracts of any size, and they can work in joint venture with non-Native companies as long as the ANC owns 51%.McCaskill has previously sponsored bills to remove those special advantages. She’s asking the SBA for a list of all such joint ventures since 2011, and for reports showing how Native communities benefitted from these contracts.Alaska Sen. Mark Begich, in a press release, says he’s tried to reason with McCaskill, a fellow Democrat. But he says she doesn’t understand Alaska history. He says ANCs shouldn’t be punished for their success.