Special operations units, especially within the United States Armed Forces, should be given orders and then specialized training to carry out missions. Units should not be given more autonomy lest they become a rogue unit that operates outside the purview of the United States government. Giving these units more autonomy creates more trouble for diplomats and may start wars if orders aren't followed strictly.
Without a checks and balance system to keep government organizations in check, it is easy for special operations organizations to take advantage of their authority and abuse their power. Historically, abuse of power has led to uprisings, tyrannies and dictatorships. Essentially, not granting more autonomy to special operations insures that proper order is maintained.