vi et armis

from Bouvier's Law Dictionary, Revised 6th Ed (1856)
VI ET ARMIS. With force and arms. When man breaks into another's close vi et 
armis, he may be opposed force by force, for there is no time to request him 
to go away. 2 Salk. 641; 8 T. R. 78, 357. 
     2. These words are universally inserted in a writ of trespass, because 
they point out that the act has been done with force, and they are technical 
words to designate this offence. Ham. N. P. 4, 10, 12; 1 Chit. Pl. 122 to 
125; and article Force. 
    

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