People on the government’s terrorist watch list tried to buy guns nearly 1,000 times in the last five years, and federal authorities cleared the purchases 9 times out of 10 because they had no legal way to stop them, according to a new government report. In one case, a person on the list was able to buy more than 50 pounds of explosives. The new statistics, compiled in a report from the Government Accountability Office that is scheduled for public release next week, draw attention to an odd divergence in federal law: people placed on the government’s terrorist watch list...