argumentum ad verecundiam (i.e., argument to authority / appeal to an expert). This is the argument that cites someone of authority who is in support of a position; and becomes a fallacious argument when that authority figure has no expertise in the subject under question.
For example, this is the old “I’m not a doctor, but I play one on TV, so I recommend you treat your hemorrhoids with product xyz, just like me!” Ok, so that is a fairly lighthearted example, but in practical use, the appeal to authority requires the listener to hold the claimant accountability. In other words, one needs to recognize the employment of the argumentum ad verecundiam and push for the qualifications of the expert being cited.
We see this tactic being used quite frequently in anthropogenic global warming debates. Rarely are actual climate scientists cited by those who deny global warming; rather scientists whose areas of expertise lie outside of climatology are cited. Even worse, authors such as Michael Crichton, due to his fictional novel the “State of Fear”, may be cited as evidence of a global warming hoax.