I am not a lawyer and I have no specific information on the facts of this case. However, it appears that the prosecutor may have been caught trying to be too cute by half. Notice that she said the knife was legal "under Maryland law". That may very well be true. But the arresting office noted that the knife was illegal under a BALTIMORE ordinance, and it was for that violation that Gray was being arrested. So what the prosecutor said may have been technically correct, it was also immaterial to the specifics of this case, and certainly could not form the basis of any of the charges against the police officers.
You make a very good point and both are listed at the end of the article. Mosby made a big deal out saying it was an illegal arrest because of that and like you say, it’s immaterial to the case in my view also.
And apparently spring assisted knives are legal in Maryland but illegal in Baltimore.
Call me a felon then. I’ve carried a spring assist for years there.
1. The arrest was under Baltimore City Code, not state.
2. As long as the knife is reasonably similar to an illegal knife, the arrest will stand up as the officer is not expected to make the final determination, that's up to the court.