President Donald Trump announced the decision to send the military to the city on September 27 this year to "protect the war-torn Portland".
According to the ruling, it violates the country's constitution and state laws to send military to the city. This is because the protests in the city should not have posed "any risk of riot" and that "ordinary law enforcement forces" can handle them on their own, the ruling states.
Trump has previously deployed the National Guard in Los Angeles and Washington DC. It is currently unclear how long the temporary blockage of sending military to Portland applies.
