Out of line

[Allieso]

When you say someone is out of line? What do you mean exactlly? And what structure is required after be out of line? Should it be follwed by any specific prepositoin?

[Tdol]

They are behaving inappropriately- they could be excessively rude/aggressive or assuming authorities they don't have, etc.

[probus]

And to answer your question, nothing needs to follow "out of line" grammatically and usually nothing does.