Nobody, my state's primaries are open, as they all should be.
But a Primary is for the party... not for the actual election of a position...
There is no good reason to vote within the system of the other party choosing their potential candidate... if you wish to do so, all you have to do is actually join the party...
Just as if it would be silly to be able to go to another state to influence their outcome, it is indeed silly to go to the process of another party to do the same thing...
And if you are so dead set to vote in the opposing party's primary, all you have to do is register within that party... not like you would be forced to vote for that party when the actual election comes...