Donald Trump has demonstrated his unsuitability to receive national security briefings due to his erratic and unprecedented behavior, which have included suggestions that Russia hack his opponent's electronic systems. He also has undisclosed financial relationships with Russia, and his campaign manager has a long-term close association with Russia and with ousted leader Viktor Yanukovych in Ukraine.
There is no legal requirement for the Office of the Director of National Intelligence to provide presidential candidates with classified information. It is a courtesy extended to candidates to get them up to speed well in advance of assuming office. The White House should prohibit Trump from receiving the typical national security briefing because of the national security risk.