In Dark Souls 2, what does this white soapstone icon mean?

In Dark Souls 2, I recently noticed this white soapstone icon. What does it mean?

Solution 1:

That sign means that you cannot invade, be invaded, summon or be summoned. The effect is probably active because you have burnt a human effigy.

After all the flame in the comments @Mondrianaire actually took the time to test it and I report here his finding:

You are correct and they are incorrect. The question was about the symbol, not about why he could not invade or be invaded. The covenant of champions does not produce this symbol. The only way to have this symbol is by actively burning an effigy, which was your answer. I have just tested this and here are two pictures, one while I was in the covenant of champions, but had not burned an effigy, and one 10 seconds later after burning one. Screenshot

Solution 2:

It appears I was wrong about the company of champions producing this symbol. Please see this comment and this answer,

The sign means you're unable to engage in any PVP (summon others, be summoned, invade others, or be invaded). You gain this effect by burning a human effigy at a bonfire. This is a temporary effect which will wear off after an hour. The symbol will only appear if the effect is gained via this method (source).