I got this off the VNEA website.
C. OPEN TABLE
The table is “open” when the choice of groups (stripes or solids) has not yet been determined. When the table is open, it is legal to hit a solid first to make a stripe or vice versa. Note: The table is always open immediately after the break shot. When the table is open it is legal to hit any solid or stripe or the 8-ball first in the process of pocketing the called stripe or solid. On an open table, all pocketed balls remain pocketed. The choice of stripes or solids is not determined on the break even if balls are made from only one or both groups. THE TABLE IS ALWAYS OPEN IMMEDIATELY AFTER THE BREAK SHOT. The choice of group is determined only when a player legally pockets a called object ball after the break shot.
The key in the above statement is in that the choice of group is determined when a player legally pockets a called object ball after the break shot. Later on when they address legal shots the say the following about safeties.
“SAFETY” SHOT: For tactical reasons a player may choose to pocket an obvious object ball and also discontinue his turn at the table by declaring “safety” in advance. A safety shot is defined as a legal shot. If the shooting player intends to play safe by pocketing an obvious object ball, then prior to the shot, he must declare a “safety” to his opponent. If this is NOT done, and one of the shooter’s object balls is pocketed, the shooter will be required to shoot again. Any ball pocketed on a safety shot remains pocketed.
So, it looks like in VNEA you can legally pocket a ball on an open table and call safe.
VNEA has a few rules that are different than BCA and some of the other leagues. For instance, in VNEA on an open table the 8ball is neutral and you can hit it first in a combination shot or carom to legally pocket a ball. Racking templates such as a magic rack are not allowed for use in Nationals. A bridge or other device cannot be used to perform a jump shot.
The rules in bold rule out calling a safe and establishing a group. They say you need to legally pocket a "called object ball", you are not calling an object ball, you are calling a safety and pocketing a ball, that is not the same thing. It is the same thing as making a ball into an uncalled pocket, which is why you can call a safe and give up the turn while making a ball. You did not "call a pocket" on the shot, therefore when you call a safe and make the ball, the ball went into an uncalled pocket, thus you give up your turn. If you are "calling the ball" to establish the group, you can't then also call a safe because one of those negates the other.
This is probably why the APA rules do not allow calling a safe and pocketing a ball, because they play slop 8 ball, so any ball going in, is a good shot for you and you keep shooting. No need to call a pocket, no need to call a safe, ball goes in, you made the shot. If you are playing called shot, you can't both call a safe and a shot because soon as you call the pocket, you made your object ball and keep shooting. Calling a safe you are NOT calling a pocket thus the ball going in is not a legally pocketed ball, and you give up your turn. A rule that would allow both just hurts my head in thinking about it, like trying to imagine infinity.
This rule is like saying "it's legal to drive over the speed limit now, but you will still get a ticket if caught".