If I were to cast Primal Command and choose to put my opponent's Stranglehold on top of his library as my first choice and search my library for a creature as my second choice, would I be able to search? Specific rules citing would be of great help. Thanks.

700.2. A spell or ability is modal if it has two or more options preceded by “Choose one —,” “Choose
two —,” “Choose one or both —,” “Choose one or more —,” or “[a specified player] chooses one
—.” Each of those options is a mode.

700.2a The controller of a modal spell or activated ability chooses the mode(s) as part of casting
that spell or activating that ability. If one of the modes would be illegal (due to an inability to
choose legal targets, for example), that mode can’t be chosen. (See rule 601.2b.)[/a specified player]

It appears to me that you couldn't even pick that mode on Primal Command because it is an illegal action at the time you were choosing modes and targets.

NullParameter wrote:It appears to me that you couldn't even pick that mode on Primal Command because it is an illegal action at the time you were choosing modes and targets.

I see where you're coming from, but I would need further verification to accept this interpretation.

100001976962891 wrote:

NullParameter wrote:It appears to me that you couldn't even pick that mode on Primal Command because it is an illegal action at the time you were choosing modes and targets.

I see where you're coming from, but I would need further verification to accept this interpretation.

It would go down like this.

1. cast Primal Command.
2. Choose bounce non creature permanent and search library.
3. Spell resolves.
4. Stranglehold bounces to opponents library.
5. You can now search your deck.

The spells abilities resolve in order of choice, and CHOOSING to search your library isn't an illegal choice.