(Portland, OR)  --  A federal judge is banning the Portland Police Bureau from using tear gas to disperse crowds of protesters.  U.S. District Judge Marco Hernandez ruled yesterday that police may only use tear gas in instances where "lives or safety of the public or police are at risk."  Hernandez also ruled police may not use tear gas to disperse crowds in cases where there is little to no risk of injury.  The order lasts for two weeks.