A U.S. judge says a customs officer improperly canceled the visa of a Russian-born scientist and Harvard University researcher charged with smuggling frog embryos in the U.S. In a ruling Tuesday, the judge said Customs and Border Protection officers have limited authority to cancel visas and can’t do so for suspected smuggling of biological samples. The U.S. Department of Homeland Security, which includes Customs and Border Protection, didn’t immediately return an email message seeking comment. Kseniia Petrova was returning from a vacation in France when she was questioned about the frog embryos while passing through customs in Boston. After an interrogation, Petrova was told her visa was being canceled.