What/who enforces the authority of stockholders?

So for context, I am in an introductory Accounting Class, and one of the things we learn is how businesses generate finances, whether internally through profits or externally via Debt/Equity Financing.

Now I understand what stock is in essence, and how being a stockholder is being part owner of a company. (Essentially the basics)

What I am curious about is how exactly a stockholder's authority is enforced, who enforces it, and what happens if the authority is ignored?

Sorry if this post belongs in another subreddit, just didn't know where to ask. Also, sorry if the flair is wrong. Thanks for the help in advanced.