Here is an excellent editorial on Reason.com:
But according to The Baltimore Sun, the police task force that investigated Gray’s death concluded the knife was covered by the city’s ban. This disagreement probably would have made it impossible to convict Rice, Miller, and Nero of false imprisonment, since that would have required proving beyond a reasonable doubt that they lacked probable cause to arrest Gray.
At the same time, if police and prosecutors cannot agree about whether Gray’s knife was legal, how was he supposed to know? It is plainly unjust to punish someone with up to a year in jail, the penalty allowed by Baltimore’s ordinance, for violating an inscrutable law.
Knife bans give cops another excuse for hassling people they deem suspicious, who are disproportionately young black men like Freddie Gray.
Asking how Gray was supposed to know if his knife was “illegal” is a really good question and once again raises the issue of how government is over-criminalizing so many aspects of life.