If you're going to invest, you do it at your own risk.
Nobody is going to protect you from your own investing decisions if you choose to do so without a) educating yourself or, b) using an investment advisor/broker to help you.
The short answer is, nothing protects you from dilution. You have no say in the matter (apart from deciding to sell your shares!).
That being said, dilution can take on many forms in its effects on a stock. Can it make your shares less valuable? By general definition, yes - anytime more of anything is available in the marketplace the less it's worth unless there's at least a reasonably equal rise in the demand for it.
Be careful about applying hard and fast rules in the stock markets though, because the moment you do that you'll find an exception (or lots of them!). Depending on the nature of the new issuance, it can have an equally beneficial effect over the longer term.
An example is when stocks split. Imagine if you'd owned Apple stock from it's initial IPO and never sold or bought any additional shares. Because of the number of splits over the years, you'd have a great many more shares than you started with, not to mention each one of those shares you own now is definitely worth more than its IPO price.
In such an instance, would you really care if your shares are "diluted" from what they were when you first bought them? I doubt it! (grin)