Logical fallacy?

"The court accepts eye witnesses as evidence. Therefore, you should accept that I saw a ghost because I have eye witnesses."

This would be a weak analogy . They are arguing that an eyewitness for a natural, everyday event (e.g., witnessing a robbery) is the same as "witnessing" a ghost. The two are not even remotely the same. We don't even need to get into the fallibility of eyewitness accounts (but see Shawn's comment if you want details on that).

While eye witness testimony is accepted as evidence in courts, the trier of fact may (and does) weigh that evidence as to reliability---a great part of which depends upon substantiating circumstances and other evidence. I put seeing ghosts with no weight as to the existence of ghosts, but quite weighty as to the mental condition or veracity of the person who claims to see them.

Eyewitness testimony is relevant to a conclusion only if the eyewitness is an authority (eyewitness) to the facts testified to.   To the extent they are not reliable, credible, or competent, to rely on such testimony is an  Appeal To Authority fallacy.

It'd be a non sequitur in my opinion.

Eye witness testimony can be accepted in court, but that doesn't mean that said witnesses can simply claim anything and get away with it. What they supposedly observed will be subject to critical examination. If they say they saw something which, for example, doesn't exist (like ghosts), it will be ignored by the court.

I'm not sure there's an actual fallacy in the way the term is used on this site (i.e., it isn't an error in reasoning, not commonly applied in arguments and not intended tone deceptive).  Having said that, the argument is very weak because of a weak analogy .  The argument is made even weaker because some terms and concepts aren't well defined or limited, making it possible for different people to understand different things from the comment.

For example, the "court accepts eye witness" testimony could be taken as meaning courts accepting anything an eye witness says just because the witness said it was so (which is not the case, making that premise false) or it could be taken as meaning that courts accept testimony about the physical items and actions that the witness observed.  

If we assume the latter and want to use someone's ghost sighting as evidence that ghosts exist, the analogy is very weak since the courts are accepting evidence about physical things and actions accepted by all to exist while the "ghost" situation doesn't involve physical items.

On the other hand, if we want to use the "ghost sighting" as acceptable evidence of someone's delusions  or of some unexplained phenomenon, the analogy would be stronger.