This is one possible interpretation, as I see it. Rome may have "confirmed the 70th Week covenant" by putting Jesus to death. That is, the Roman ruler adjudicated at Jesus' trial, delivering him to be executed, thus fulfilling biblical prophecy. In the midst of the 70th Week Pilate ended the sacrifices of the Law by putting the Messiah to death, thus rendering the Law nil.
Jesus, the Messiah, was said to come *after* the 69 Weeks. Thus, he came in the 70th Week to fulfill the covenant in his death. It was then, after the 70th Week was completed in the midst of that Week that the Roman Army came to desolate the city and the sanctuary, which was in 70 AD.
Dan 9.26 After the sixty-two ‘sevens,’ the Anointed One [Messiah] will be put to death and will have nothing. The people of the ruler who will come [Rome] will destroy the city and the sanctuary [70 AD]. The end will come like a flood: War will continue until the end, and desolations have been decreed. 27 He [Rome] will confirm a covenant [fulfill the Law] with many for one ‘seven.’ In the middle of the ‘seven’ he will put an end to sacrifice and offering [invalidate the Law]. And at the temple he will set up an abomination that causes desolation [the Roman Army], until the end that is decreed is poured out on it [the 70 AD destruction of the temple].
I consider this a very possible interpretation. Vs. 27 is a recapitulation of vs. 26.
Vs. 26: After 69 Weeks--Messiah in the 70th Week. Messiah killed. Jerusalem destroyed.
Vs. 27: Rome confirms biblical prophecy of the Messiah in the 70th Week. Temple destroyed.