No they do not.

There is explicitly Delaware case law where shareholders sued company for not exploiting tax loophole.

Shareholders lost, company won.

There is no legal obligation for directors to maximise profit.

I don't know if shareholders would take the drastic route of sueing Apple rather than pressuring them to fire the CFO that didn't use every tax loophole and replace him with one who does. The big holders[1] of stock like Vanguard, Blackrock, etc could influence other shareholders to vote a certain way and elect a new Board of Directors... the directors then fire the CFO and hire one who channels revenue through Ireland so they can save billions of dollars. That way, they can compete with the other companies[2] like Microsoft/Google/Oracle/etc using the aggressive tax avoidance strategies to save billions.

[1]https://finance.yahoo.com/quote/AAPL/holders?p=AAPL

[2]https://en.wikipedia.org/wiki/Double_Irish_arrangement#Compa...