There are two different issues here.
1) Certification of the election by the Massachusetts SoS. Apparently, there is a legal basis for him doing so under State law
2) Voting by Kirk after 1/19/10. There is some legal background under the U. S. Constitution for denying him a vote after the polls are closed on the 19th
If Reid allows Kirk to vote after the 19th, there will likely by a serious constitutional challenge to any bill that passes as a result.
Still, IMHO,as a proponent and signatory of the law in 1912 Mass. should be bound by elections. If they subvert those elections is the result constitutional?