Which rules are those and are you sure this Act doesn't overrule them?
i’m not aware of anything within the act which refers to the 1970 breaking of communion with the OCa specifically.
The ROCOR’s 1971 reaction was thus as follows:
The Council of Bishops, having listened to the report of the Synod of Bishops concerning the so-called Metropolia’s having received autocephaly from the Patriarchate of Moscow, approves all the steps taken in due course by the Synod of Bishops to convince Metropolitan Irinei and his colleagues of the perniciousness of a step which deepens the division which was the result of the decision of the Cleveland Council of 1946 which broke away from the Russian Orthodox Church Outside of Russia.
The American Metropolia has received its autocephaly from the Patriarchate of Moscow, which has not possessed genuine canonical succession from His Holiness Patriarch Tikhon from the time when Metropolitan Sergii, who later called himself Patriarch, violated his oath with regard to Metropolitan Petr, the locum tenens of the patriarchal throne, and set out upon a path which was then condemned by the senior hierarchs of the Church of Russia. Submitting all the more to the commands of the atheistic, anti-Christian regime, the Patriarchate of Moscow has ceased to be that which expresses the voice of the Russian Orthodox Church. For this reason, as the Synod of Bishops has correctly declared, none of its acts, including the bestowal of autocephaly upon the American Metropolia, has legal force. Furthermore, apart from this, this act, which affects the rights of many Churches, has elicited definite protests on the part of a number of Orthodox Churches, who have even severed communion with the American Metropolia.
Viewing this illicit act with sorrow, and acknowledging it to be null and void, the Council of Bishops of the Russian Orthodox Church Outside of Russia, which has hitherto not abandoned hope for the restoration of ecclesiastical unity in America, sees in the declaration of American autocephaly a step which will lead the American Metropolia yet farther away from the ecclesiastical unity of the Church of Russia. Perceiving therein a great sin against the enslaved and suffering Church of Russia, the Council of Bishops DECIDES: henceforth, neither the clergy nor the laity [of the Russian Church Abroad] are to have communion in prayer or the divine services with the hierarchy or clergy of the American Metropolia.[11]
orthodoxwiki
Here’s the oca stance: (which notably has no mention from Moscow)
http://www.oca.org/Docs.asp?ID=170&SID=12