I'm opposed to the drone strikes, but there is a clear difference here. In the case of these fishy vessels, they could be detained and boarded. It's not really a high risk situation, and it's something the Navy and Coast Guard are trained to do.

In the case of alleged terrorists being targeted by drone strikes, it would be risky in many cases to try to apprehend those individuals. They are in foreign countries or parts thereof which are not under U.S. control or control of an ally.